Unit 3
Concept of Global Warming and Climate

Learning Outcomes

Prerequisites

Key words

Climate change, Global warming, Greenhouse gases, Acid rain, Ozone layer, Aerosols.

Discussion

What is the current temperature in your place? Have you heard from your grandparents that today’s temperature is more than that of the temperature during their childhood? Do you know why it happens?

4.3.1 Global Warming and Climate Change

Global warming is considered to be one of the central environmental issues in the recent years. It may prove to be very problematic and disastrous causing severe harm to the biotic and abiotic components of the environment. Nitrogen and oxygen are the main constituents of the atmosphere but the proportion of other gases such as carbon dioxide and carbon monoxide are steadily increasing. Because of the increasing presence of these gases, there is an increase in the global temperature. In other words the earth surface is getting warmer and warmer. Sunlight enters the earth’s atmosphere and after hitting the earth’s surface gets radiated back into the atmosphere. Here it is absorbed by certain naturally present gases such as carbon dioxide. This absorption process heats the atmosphere and thus warms the earth’s surface. When the gases are present in normal proportions the warming of the earth is normal and their presence is very essential and is responsible for the existence of life on earth. However, when the proportion of these gases increases, these gases allow the sun-light reflect back to the atmosphere, resulting in heat generation. Over a period of time the temperature of the earth will increase gradually. This phenomenon is called as global warming. Global warming is also known as the greenhouse effect because the phenome-non is very similar to what happens in a green house. The effect of this increase in temperature is damaging the environment.

4.3.2 Implications of global warming

1. Global warming can drastically reduce the moisture levels in current fertile zones and turn them subsequently into dry lands and desert.
2. Many countries in the world will suffer from droughts.
3. The agricultural production will be minimized to a significant extent.
4. Global warming will automatically lead to rise in temperature. According to the intergovernmental panel on climatic change set up by the United Nations Environmental Program in 1998, the world is already 0.5 Celsius warmer than the pre-industrial period and this rise in temperature will be an ongoing process.
5. Global warning has a more drastic effect. A rise in temperatures would result in the melting at Polar Regions. This will lead to rise in the sea- levels. Even a 5% rise in sea – level would lead to displacement of millions of people in low tide areas and a number of Small Island nations will disappear totally.
6. Others important effects include global mean surface warming, polar winter surface warm in reduction of sea -ice g, etc.
7. One of the most severe effects of global warming from a human perspective is the creation of ‘Climate refugees’. Climate refugees are those people who suffer from climatic conditions such as drought, floods, starvations, displacement etc. These climate refugees therefore signify the most visible symbol of global warming.

4.3.3 Major drivers of climate change (greenhouse gases and aerosols)

Larger emissions of greenhouse gases lead to higher concentrations in the atmosphere. Greenhouse gas concentrations are measured in parts per million, parts per billion, and even parts per trillion. One part per million is equivalent to one drop of water diluted into about 13 gallons of liquid (roughly the fuel tank of a compact car). Each of these gases can remain in the atmosphere for different amounts of time, ranging from a few years to thousands of years. All of these gases remain in the atmosphere long enough to become well mixed.

We will discuss some important greenhouse gases in the atmosphere;

1. Water Vapour
   The most abundant greenhouse gas overall, water vapor differs from other greenhouse gases in that changes in its atmospheric concentrations are linked not to human activities directly, but rather to the warming that results from the other greenhouse gases emitted. As the temperature of the atmosphere rises, more water is evaporated from ground storage (rivers, oceans, reservoirs, soil). Because the air is warmer, the absolute humidity can be higher (in essence, the air is able to ‘hold’ more water when it’s warmer), leading to more water vapour in the atmosphere. As a greenhouse gas, the higher concentration of water vapour the more thermal IR energy radiated from the Earth, thus further warming the atmosphere. The warmer atmosphere can then hold more water vapour and so on and so on. This is referred to as a ‘positive feedback loop’.
2. Carbon dioxide
   Carbon dioxide (CO2) is the primary green-house gas emitted through human activities. Carbon dioxide is naturally present in the atmosphere and forms part of the Earth’s carbon cycle (the natural circulation of carbon among the atmosphere, oceans, soil, plants, and animals). Human activities are altering the carbon cycle–both by adding more CO2to the atmosphere, and by influencing the ability of natural sinks, like forests and soils, to remove and store CO2 from the atmosphere. While CO2 emissions come from a variety of natural sources, human-related emissions are responsible for the increase that has occurred in the atmosphere since the industrial revolution. The main human activity that emits CO2is the combustion of fossil fuels (coal, natural gas, and oil) for energy and transportation, although certain industrial processes and land-use changes also emit CO2. Carbon dioxide is constantly being exchanged among the atmosphere, ocean, and land surface as it is both produced and absorbed by many microorganisms, plants, and animals. However, emissions and removal of CO2 by these natural processes tend to balance the impacts. Since the Industrial Revolution began around 1750, human activities have contributed substantial-ly to climate change by adding CO2 and other heat-trapping gases to the atmosphere.
3. Methane
   Although methane (CH4) persists in the atmosphere for far less time than carbon dioxide (about a decade), it is much more potent in terms of the greenhouse effect. Human activities emitting methane include leaks from natural gas systems and the raising of livestock. Methane is also emitted by natural sources such as natural wetlands. In addition, natural processes in soil and chemical reactions in the atmosphere help remove CH4 from the atmosphere. Methane’s lifetime in the atmosphere is much shorter than carbon dioxide (CO2), but CH4 is more efficient at trapping radiation than CO2.The comparative impact of CH4 is 25 times greater than CO2 over a 100-year period.
4. Nitrous oxide
   Human activities such as agriculture, fuel combustion, wastewater management, and industrial processes are increasing the amount of N2O in the atmosphere. Nitrous oxide is also naturally present in the atmosphere and forms the Earth’s nitrogen cycle, and has a variety of natural sources. Nitrous oxide molecules stay in the atmosphere for an average of 114 years before being removed by a sink or destroyed through chemical reactions. The impact of 1 pound of N2O on warming the atmosphere is almost 300 times that of 1 pound of carbon dioxide. Globally, about 40 percent of total N2O emissions come from human activities. Nitrogen takes on a variety of chemical forms throughout the nitrogen cycle, including N2O. Natural emissions of N2O are mainly from bacteria breaking down nitrogen in soils and the oceans. Nitrous oxide is removed from the atmosphere when it is absorbed by certain types of bacteria or destroyed by ultraviolet radiation or chemical reactions.
5. Fluorocarbons (FCs)
   Unlike many other greenhouse gases, fluorinated gases have no natural sources and only come from human-related activities. They are emitted through their use as substitutes for ozone-depleting substances (e.g., as refrigerants) and through a variety of industrial processes such as aluminium and semiconductor manufacturing. Many fluorinated gases have very high global warming potentials (GWPs) relative to other greenhouse gases, so small atmospheric concentrations can have disproportionately large effects on global temperatures. They can also have long atmospheric lifetimes in some cases, lasting thousands of years. Like other long-lived greenhouse gases, most fluorinated gases are well-mixed in the atmosphere, spreading around the world after they are emitted. Many fluorinated gases are removed from the atmosphere only when they are destroyed by sunlight in the far upper atmosphere. In general, fluorinated gases are the most potent and longest lasting type of greenhouse gases emitted by human activities. There are four main categories of fluorinated gases—hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), sulphurhexafluoride (SF6), and nitrogen trifluoride (NF3).

4.3.4 Green House Effect

The greenhouse effect happens when certain gases—known as greenhouse gases—collect in Earth’s atmosphere. These gases, which occur naturally in the atmosphere, include carbon dioxide, methane, nitrogen oxide, and fluorinated gases such as chlorofluorocarbons (CFCs).

Due to sun rays, earth surface gets heated. Subsequently it cools and the heat is radiated from the earth to the atmosphere. But CO2 and other heat absorbing gases take a part of the radiated heat and return it to the earth. This process results in the accumulation of extra heat energy at the surface of the earth. In the last few decades, the amount of heat absorbing gases has remarkably increased and as a result the average temperature of the atmosphere has gone up. This phenomenon is called “Green House Effect”. It is clear that gases like CO2, Chloroflurocarbons, N2O and CH4 make a cloud over the earth, which allows the incoming rays of the sun but obstructs the outgoing heat energy from the earth to the atmosphere. There have been numerous warnings in the recent years that the earth’s climatic pattern which almost maintained a steady course for centuries has undergone visible changes. This is caused by changes in the composition of global atmosphere which consists of a number of natural and synthetic gases. Any increase in gases which have the ability to absorb infrared radiation reflected will enhance heat – trapping capacity of the earth. In 1961, the English Philospher John Tyndoll proposed that increased concentration of atmospheric carbon dioxide could raise surface temperature and change the climate. Since then, the concentration of this gas has increased by about 25%. This increase has been caused by various factors. An indiscriminate burning of fossil fuels like coal, oil and natural gases releases huge amounts of gas into the atmosphere. There are more than half a billion vehicles on the road which spew CO2 and other gases into air. The burning of a large number of oil wells continuously after the gulf war has added tremendous amount of carbon dioxide into the atmosphere. As far as industrial revolution is concerned the main culprits are the developed countries. The industrialized countries are responsible for forcing the pace of global warming, and climatic changes. The entire international community from world leaders and to layman is aware of global warming and its dangers. This could destabilize world food security. There may be massive disruption to agriculture and loss of ecosystem of word wide importance.

4.3.5 Major impacts of climate change on agriculture

Climate change and agriculture are interrelated processes, both of which take place on a global scale. Climate change affects farming in a number of ways, including through changes in average temperatures, rainfall, and climate extremes (e.g. heat waves), changes in pests and diseases, changes in atmospheric carbon dioxide and ground-level ozone concentrations, changes in the nutritional quality of some foods and changes in sea level. Climate change is already affecting agriculture, with effects unevenly distributed across the world.

The accelerating pace of climate change, combined with global population and income growth, threatens food security everywhere. Agriculture is extremely vulnerable to climate change. Higher temperatures eventually reduce yields of desirable crops while encouraging weed and pest proliferation. Pests management becomes less effective, meaning that higher rates of pesticides will be necessary to achieve the same levels of control. Heat wave s can cause extreme heat stress in crops, which can limit yields if they occur during certain times of the plants’ life-cycle (pollination, pod or fruit set). Also, heat waves can result in wilted plants (due to elevated transpiration rates) which can cause yield loss if not counteracted by irrigation. Heavy rains that often result in flooding can also be detrimental to crops and to soil structure. Most plants cannot survive in prolonged waterlogged conditions because the roots need to breathe. The overall impacts of climate change on farming are expected to be negative, threatening global food security.

Changes in climate may also impact the water availability and water needs for farming. If temperature increases and more sporadic rainfall events result from global warming, it is possible that irrigation needs could increase in the future. In anticipation of these changes, plant breeders are currently working to develop new varieties of crops that are considered to be drought tolerant, and more adaptable to varying levels of temperature and moisture.

4.3.5.1 Impacts on crops

• Higher CO2 levels can affect crop yields. Some laboratory experiments suggest that elevated CO2 levels can increase plant growth. However, other factors, such as changing temperatures, ozone, water and nutrient constraints, may counteract these potential increases in yield. For example, if temperature exceeds a crop’s optimal level, if sufficient water and nutrients are not available, yield increases may be reduced or reversed. Elevated CO2 has been associated with reduced protein and nitrogen content in alfalfa and soybean plants, resulting in a loss of quality. Reduced grain and forage quality can reduce the ability of pasture and rangeland to support grazing livestock.
• More extreme temperature and precipitation can prevent crops from growing. Extreme events, especially floods and droughts, can harm crops and reduce yields. For example, in 2010 and 2012, high night time temperatures affected corn yields across the U.S. Corn Belt, and premature bud-ding due to a warm winter caused $220 million in losses of Michigan cherries.
• Dealing with drought could be-come a challenge in areas where rising summer temperatures cause soils to become drier. Al-though increased irrigation might be possible in some places, in other places water supplies may also be reduced, leaving less water available for irrigation when more is needed.
• Many weeds, pests, and fungi thrive under warmer temperatures, wetter climates, and increased CO2 levels. The ranges and distribution of weeds and pests are likely to increase with climate change. This could cause new problems for farmers’ crops previously unexposed to these species.
• Though rising CO2 can stimulate plant growth, it also reduces the nutritional value of most food crops. Rising levels of atmospheric carbon dioxide reduce the concentrations of protein and essential minerals in most plant species, including wheat, soy-beans, and rice. This direct effect of rising CO2 on the nutritional value of crops represents a potential threat to human health. Hu-man health is also threatened by increased pesticide use due to in-creased pest pressures and reductions in the efficacy of pesticides.

4.3.5.2 Impacts on livestock

• Heat waves directly threaten live-stock. Heat stress affects animals both directly and indirectly. Over-time, heat stress can increase vulnerability to disease, reduce fertility and reduce milk production.
• Drought may threaten pasture and feed supplies. Drought reduces the amount of quality forage available to grazing livestock. Some areas could experience longer, more intense droughts, resulting from higher summer temperatures and reduced precipitation. For animals that rely on grain, changes in crop production due to drought could also become a problem.
• Climate change may increase the prevalence of parasites and diseases that affect livestock.. In areas with increased rainfall, moisture-reliant pathogens could thrive.
• Potential changes in veterinary practices, including an increase in the use of parasiticides and other animal health treatments, are likely to be adopted to maintain livestock health in response to climate-induced changes in pests, parasites, and microbes. This could increase the risk of pesticides entering the food chain or lead to evolution of pesticide resistance, with subsequent implications for the safety, distribution, and consumption of livestock and aquaculture products.
• Increases in carbon dioxide (CO2) may increase the productivity of pastures, but may also decrease their quality. Increases in atmospheric CO2 can increase the productivity of plants on which live-stock feed. However, the quality of some of the forage found in pasturelands decreases with higher CO2. As a result, cattle would need to eat more to get the same nutritional benefits.

4.3.5.3 Impacts on Fisheries

• Many aquatic species can find colder areas of streams and lakes or move north along the coast or in the ocean. Nevertheless, moving into new areas may put these species into competition with other species over food and other re-sources.
• Some marine disease outbreaks have been linked with changing climate. Higher water temperatures and higher estuarine salinities have enabled an oyster para-site to spread farther north along the Atlantic coast.
• Changes in temperature and seasons can affect the timing of reproduction and migration. Many steps within an aquatic animal’s lifecycle are controlled by temperature and the changing of the seasons.

4.3.6 Major impacts of climate change on forest

Climate changes directly and indirectly affect the growth and productivity of forests through changes in temperature, rainfall, weather, and other factors. In addition, elevated levels of carbon dioxide have an effect on plant growth. These changes influence complex forest eco-systems in many ways.

4.3.6.1 Impacts on Forest Growth and Productivity

• Warming temperatures generally increase the length of the growing season. It also shifts the geo-graphic ranges of some tree species. Habitats of some types of trees are likely to move north or to higher altitudes. Other species will be at risk locally or region-ally if conditions in their current geographic ranges are no longer suitable.
• Climate change will increase the risk of drought in some areas and the risk of extreme precipitation and flooding in others. Increased temperatures alter the timing of snowmelt, affecting the seasonal availability of water. Although many trees are resilient to some degree of drought, increases in temperature could make future droughts more damaging than those experienced in the past. In addition, drought increases wildfire risk, since dry trees and shrubs provide fuel to fires.
• Given sufficient water and nutrients, increases in atmospheric CO2 may enable trees to be more productive, which may change the distribution of tree species. Growth will be highest in nutrient-rich soils with no water limitation, and will decrease with decreasing fertility and water supply.

4.3.6.2 Impacts of Forest Disturbances

• Climate change could alter the frequency and intensity of forest disturbances such as insect out-breaks, invasive species, wildfires and storms. These disturbances can reduce forest productivity and change the distribution of tree species. In some cases, forests can recover from a disturbance. In other cases, existing species may shift their range or die out. In these cases, the new species of vegetation that colonize the area create a new type of forest.
• Disturbances can interact with one another, or with changes in temperature and precipitation, to increase risks to forests. For example, drought can weaken trees and make a forest more susceptible to wildfire or insect outbreaks. Similarly, wildfire can make a forest more vulnerable to pests.

4.3.6.3 Impact of Climate Change on Forest Sector

• Change in Supply- Climate change can increase global timber production through location changes of forests, i.e., through a shift towards the poles of the most important for forestry species. Climate change can also accelerate vegetation growth caused by a warmer climate, longer growth seasons, and elevated atmospheric CO2 concentrations. Changing timber supply will affect the market, generally lowering prices. It will also impact supply for other uses, e.g., enhancing the potential of using various types of wood biomass energy.
• Change in Demand- Some model-based estimates project an in-crease in biofuel demand during the next 50 years. The use of wood for fuel and biomass energy could dramatically escalate in the face of rising energy prices and new technologies.

4.3.7 Major impacts of climate change on Water resources

Water resources are important to both society and ecosystems. We depend on a reliable, clean supply of drinking water to sustain our health. We also need water for agriculture, energy production, navigation, recreation, and manufacturing. Many of these uses put pressure on water resources, stresses that are likely to be exacerbated by climate change.

1. Water Cycle and Water Demand
   Warmer temperatures increase the rate of evaporation of water into the atmosphere, in effect increasing the atmosphere’s capacity to “hold” water. Increased evaporation may dry out some areas and fall as excess precipitation on other areas. Changes in the amount of rain falling during storms provide evidence that the water cycle is already changing.
2. Water supply
   Low water and droughts have severe consequences on most sectors, particularly agriculture, forestry, energy, and drinking water provision. Activities that depend on high water abstraction and use, such as irrigated agriculture, hydropower generation and use of cooling water, will be affected by changed flow regimes and reduced annual water availability. Climate change tends to increase the frequency and intensity of rainfall; there may be an increase in the occurrence of flooding due to heavy rainfall events. Groundwater re-charge may also be affected with a reduction in the availability of groundwater for drinking water in some regions.
3. Water Quality
   Water quality could suffer in areas experiencing increases in rainfall. Heavy precipitation events could cause problems for the water infrastructure, as sewer systems and water treatment plants are overwhelmed by the increased volumes of water. Heavy downpours can increase the amount of runoff into rivers and lakes, washing sediment, nutrients, pollutants, trash, animal waste, and other materials into water supplies, making them unusable, unsafe, or in need of water treatment.

Freshwater resources along the coastal area face risks from sea level rise. As the sea rises, saltwater moves into freshwater areas. This may force water managers to seek other sources of fresh water, or increase the need for desalination (or removal of salt from the water) for some coastal freshwater aquifers used as drinking water supply.

Drought can cause coastal water resources to become more saline as freshwater supplies from rivers are reduced. Water infrastructure in coastal cities, including sewer systems and wastewater treatment facilities, faces risks from rising sea levels and the damaging impacts of storm surges.

4.3.8 Management options to tackle climate change

1. The global warming is largely the product of industrialized nations and they are the world’s largest energy users, CFC producers and consumers, Car manufacturing and use as well as use of nitrogen fertilizers have resulted in global warming and hence the solution is a radical re-thinking of the whole western industrialized lifestyle. However, this solution is almost impossible because it involves a lot of sacrifice by the industrialized world.
2. The immediate solution to reduce global warming is to reduce carbon dioxide emission; this is possible by closing down fossil fuel, power stations and replace by nuclear power.
3. Industrialized nations will assist the developing countries in obtaining data in limiting emissions.
4. All the countries must implement national strategies to limit their toxic emissions.
5. Countries should be encouraged to recognize climatic changes in the formulation of economic, social and environmental policies.
6. It is necessary to increase public awareness related to environmental problems especially global warming through conscious efforts of education and training.
7. All the countries will co-operate and participate in a continues international research and effort
8. It is necessary to have global environmental ethics to protect the earth from any further exploitation in the nature of development and modernization. Hence environmental movements are necessary in all parts of the world monotony to consume the natural resources but also to share them equitably and fairly. This will sustain earth to a significant extension.

4.3.9 Over view of Acid rains

Acid precipitation has been known for centuries in areas such as London where sulphur discharged by the burning of coal produces toxic smogs. However, the problem did not assume scientific, economic and political prominence until the early 1980s. As it transcends national boundaries, the acid rain problem has become a subject of heated controversy be-tween otherwise friendly neighbours like the US and Canada or Germany and the Scandinavian countries. It has been found that acid precipitation is harmful to trees and other forms of vegetation, causing foliar injury and reduction in growth. The primary reason that acid rain has received attention is its economic impact. The cost to control emission of sulphur compounds from power plants, refineries and smoke generating industries is enormous. The problem of acid rain is more apparent in the parts of the world which are industrialised. The western countries and other developing countries of the world are severely facing this problem. Among Indian cities the possibility of acid rain has increased in Mumbai, Delhi, Kanpur, Bangalore, Ahmedabad and Calcutta. Acid rain has adversely affected the entire ecosystem. Due to acid rain, the mineral balance in forests, rivers, fields and lakes is being disturbed. There is decrease in productivity. The resistance power of the lives at the surface of water has also decreased. The microorganisms have gradually become inactive and it has affected the natural cycles of elements. It has not only affected the human life but also of thousands of species in water. The most important thing is to reduce CO2, SO2 and NO2 gases in the atmosphere to stop acid rain. It should be our endeavour to limit the elements helping acid rain. We must also regulate the spread of the gases in the atmosphere.

4.3.10 Ozone layer depletion

The Earth’s atmosphere is composed of several layers. The lowest layer, the troposphere, extends from the Earth’s surface up to about 6 miles or 10 km in altitude. Most atmospheric ozone is concentrated in a layer in the stratosphere, about 9 to 18 miles (15 to 30 km) above the Earth’s surface. Ozone is a molecule that contains three oxygen atoms. At any given time, ozone molecules are constantly formed and destroyed in the stratosphere. The total amount has remained relatively stable during the decades that it has been measured. It has the potential to absorb around 97-99% of the harmful ultraviolet radiations coming from the sun that can damage life on earth.

Ozone layer depletion is the thinning of the ozone layer present in the upper atmosphere. This happens when the chlorine and bromine atoms in the atmosphere come in contact with ozone and destroy the ozone molecules. One chlorine can destroy 100,000 molecules of ozone. It is destroyed more quickly than it is created. Some compounds release chlorine and bromine on exposure to high ultraviolet light, which then contributes to the ozone layer depletion. Such compounds are known as Ozone Depleting Substances (ODS).
The ozone-depleting substances that contain chlorine include chlorofluorocarbon, carbon tetrachloride, hydrochlorofluorocarbons, and methyl chloroform, whereas, the ozone-depleting substances that contain bromine are halons, methyl bromide, and hydro bromofluorocarbons. Chlorofluorocarbons are the most abundant ozone-depleting substance. It is only when the chlorine atom reacts with some other molecule, it does not react with ozone.
In the 1970s, concerns about the effects of ozone-depleting substances (ODS) on the stratospheric ozone layer prompted sever-al countries, including the United States, to ban the use of chlorofluorocarbons (CFCs) as aerosol propellants. However, global production of CFCs and other ODS continued to grow rapidly as new uses were found for these chemicals in refrigeration, fire suppression, foam insulation, and other applications. Some natural processes, such as large volcanic eruptions, can have an indirect effect on ozone levels. For example, Mt. Pinatubo’s 1991 eruption did not increase stratospheric chlorine concentrations, but it did produce large amounts of tiny particles called aerosols (different from consumer products also known as aerosols). These aerosols increase chlorine’s effectiveness at destroying ozone. The aerosols in the stratosphere create a surface on which CFC-based chlorine can destroy ozone. However, the effect from volcanoes is short-lived.
One example of ozone depletion is the annual ozone “hole” over Antarctica that has occurred during the Antarctic spring since the early 1980s. This is not really a hole through the ozone layer, but rather a large area of the stratosphere with extremely low amounts of ozone. The Montreal Protocol was proposed in 1987 to stop the use, production and import of ozone-depleting substances and minimise their concentration in the atmosphere to protect the ozone layer of the earth.

4.3.11 Effects of Ozone Layer Depletion

The depletion of the ozone layer has harm-ful effects on the environment. Let us see the major effects of ozone layer depletion on man and environment.
Effects on Human Health
The humans will be directly exposed to the harmful ultraviolet radiations of the sun due to the depletion of the ozone layer. This might result in serious health issues among humans, such as skin diseases, cancer, sunburns, cataract, quick ageing and weak immune system.
Effects on Animals
Direct exposure to ultraviolet radiations leads to skin and eye cancer in animals.
Effects on the Environment
Strong ultraviolet rays may lead to mini-mal growth, flowering and photosynthesis in plants. The forests also have to bear the harmful effects of the ultraviolet rays.
Effects on Marine Life
Planktons are greatly affected by the exposure to harmful ultraviolet rays. These are higher in the aquatic food chain. If the planktons are destroyed, the organisms present in the food chain are also affected.

Recap

Objective type questions

Answer to Objective type questions

Self Assessment Questions

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Reference