Greenhouse effect and global warming

Correct answer: A. Because weather and most climate processes occur there

Explanation: The troposphere is the lowest layer of Earth’s atmosphere and contains most atmospheric mass and water vapour. Clouds, weather, convection, and many important climate interactions occur there. Greenhouse gases in this layer absorb and re-emit outgoing infrared radiation, influencing surface temperature. It is not Earth’s core, ocean floor, or a lunar layer.

Correct answer: A. Burning more fossil fuels

Explanation: Burning coal, oil, or natural gas releases carbon dioxide and can also produce other greenhouse gases and pollutants. Increasing fossil-fuel combustion for electricity, transport, industry, or heating therefore raises emissions. Saving energy, planting and protecting trees, and using solar energy can generally reduce emissions when implemented responsibly, so burning more fossil fuels is the correct choice.

Correct answer: A. Cycling or walking

Explanation: Cycling or walking for suitable short journeys can replace a trip by a motor vehicle and therefore reduce fuel consumption, exhaust emissions, traffic, and noise. The actual benefit depends on distance, safety, and available transport choices, but it is a recognised low-carbon behaviour. Burning waste, wasting electricity, or unnecessary driving generally increases pollution or energy use.

Correct answer: A. It can absorb heat radiation

Explanation: Carbon dioxide is a greenhouse gas that absorbs particular wavelengths of outgoing longwave, or infrared, radiation emitted by Earth’s surface. It then re-emits energy in different directions, including back toward the surface and lower atmosphere. Increasing atmospheric carbon dioxide strengthens the greenhouse effect and contributes to warming; it does not control rivers, form the Moon, or remove gravity.

Correct answer: A. Climate and atmosphere

Explanation: The greenhouse effect and global warming are studied mainly through climate science and atmospheric science. These fields examine atmospheric gases, radiation, temperature, weather and climate processes, energy balance, and long-term environmental change. Geography also studies their spatial patterns and human consequences, but the most direct field among the options is climate and atmosphere.

Correct answer: B. Greenhouse gases

Explanation: Greenhouse gases such as water vapour, carbon dioxide, methane, nitrous oxide, and ozone absorb and re-radiate outgoing infrared radiation. This process retains heat in the lower atmosphere and makes Earth warmer than it would be without an atmosphere. The natural greenhouse effect supports life, while human activities have increased greenhouse-gas concentrations and intensified warming. Therefore, greenhouse gases are the correct answer.

Correct answer: A. Rise in Earth's average temperature

Explanation: Global warming means the long-term increase in Earth's average surface temperature. It is mainly associated with the enhanced greenhouse effect caused by rising concentrations of gases released through fuel burning, deforestation and industrial activities. It can influence rainfall and weather patterns.

Correct answer: C. Carbon dioxide

Explanation: Carbon dioxide is the principal contributor to current human-caused global warming because large quantities are emitted by burning coal, oil and natural gas, as well as by deforestation and cement production. It absorbs outgoing infrared radiation and remains influential for a long time.

Correct answer: C. Carbon dioxide

Explanation: Carbon dioxide is a major greenhouse gas. It absorbs outgoing infrared radiation and re-emits some energy, reducing the rate at which heat escapes to space. Human activities, especially fossil-fuel combustion and deforestation, have increased atmospheric carbon dioxide and intensified warming.

Correct answer: B. Absorb outgoing infrared heat and retain it in the atmosphere

Explanation: Greenhouse gases, including carbon dioxide, methane and water vapour, absorb infrared radiation emitted by Earth's surface and re-radiate part of it in different directions, including downward. This slows heat loss to space and warms the lower atmosphere; they do not block all escaping heat.

Correct answer: D. They are different issues, but both are related to the atmosphere

Explanation: Ozone depletion and global warming are different atmospheric issues. Stratospheric ozone absorbs harmful ultraviolet radiation, whereas global warming is mainly driven by increased greenhouse gases such as carbon dioxide and methane. Some substances can affect both issues, but ozone depletion is not the direct main cause of global warming.

Correct answer: A. Earth's average temperature would fall drastically

Explanation: The natural greenhouse effect retains part of Earth's outgoing heat and keeps the average surface temperature suitable for life. Without it, Earth's mean temperature would be far lower and much surface water could freeze. Excessive warming results from an enhanced greenhouse effect, not from its absence.

Correct answer: A. Melting of glaciers

Explanation: Global warming raises average temperatures on land and in the oceans. As a result, glaciers and ice sheets can lose mass more rapidly, and meltwater from land ice contributes to sea-level rise. Earthquakes are mainly tectonic, while rotation and the day-night cycle do not end because of warming.

Correct answer: A. Natural

Explanation: The greenhouse effect is a natural atmospheric heating process. Gases such as water vapour, carbon dioxide and methane absorb some outgoing infrared radiation and keep Earth's surface warmer than it would otherwise be. Human activities enhance this natural effect, causing additional global warming.

Correct answer: A. CH₄

Explanation: Methane has the molecular formula CH₄, meaning that each molecule contains one carbon atom bonded to four hydrogen atoms. It is a greenhouse gas released from sources such as wetlands, livestock digestion, landfills and fossil-fuel production. CO₂ is carbon dioxide, not methane.

Correct answer: A. Burning of fossil fuels

Explanation: Burning coal, petroleum and natural gas releases carbon that had been stored underground for millions of years, producing large quantities of atmospheric CO₂. Although natural carbon-cycle processes also exchange CO₂, sea waves and cloud condensation are not major causes of the recent human-driven increase.

Correct answer: B. Deforestation

Explanation: Deforestation removes trees that absorb carbon dioxide through photosynthesis and often releases stored carbon when vegetation is burned or decomposes. The resulting increase in atmospheric CO₂ strengthens the greenhouse effect. Tree planting, water conservation and soil conservation generally support environmental protection rather than directly increasing warming.

Correct answer: A. Carbon dioxide

Explanation: Carbon dioxide is the most important long-lived greenhouse gas driving present human-caused warming. Its concentration increases through fossil-fuel combustion, deforestation and cement manufacture. Oxygen, nitrogen and argon are abundant atmospheric gases, but they do not absorb infrared radiation strongly enough to be the main cause of this warming.

Correct answer: B. Increase temperature

Explanation: When concentrations of carbon dioxide, methane and other greenhouse gases rise, the atmosphere absorbs more outgoing infrared radiation and sends more energy back toward the surface. This enhanced heat trapping raises average global temperature. It does not directly stop Earth's rotation or simply increase atmospheric pressure.

Correct answer: A. Methane

Explanation: Methane is produced during anaerobic digestion in the stomachs of ruminants such as cattle, buffaloes and sheep. Much of it is released through belching and some comes from manure. Methane is a powerful greenhouse gas, so livestock emissions contribute to global warming.

Correct answer: B. Greenhouse effect

Explanation: The greenhouse effect is the atmospheric process in which greenhouse gases absorb and re-emit part of Earth's outgoing infrared radiation, reducing heat loss to space. Reflection sends radiation back, evaporation changes liquid water to vapour, and condensation changes vapour into liquid or ice.

Correct answer: A. Greenhouse gases

Explanation: Greenhouse gases such as carbon dioxide, methane, nitrous oxide and water vapour absorb particular wavelengths of outgoing infrared radiation and re-emit energy within the atmosphere. This heat-trapping process warms the lower atmosphere. The other groups do not describe the main gases responsible for this effect.

Correct answer: A. Using renewable energy

Explanation: Solar, wind and other renewable energy sources can replace some electricity generated by burning coal, oil or gas. This reduces carbon dioxide and other greenhouse-gas emissions when managed appropriately. Burning more coal, increasing unnecessary vehicle use and deforestation generally increase emissions and warming.

Correct answer: A. Agriculture

Explanation: Global warming can affect agriculture by changing temperature, rainfall, growing seasons, soil moisture, pest ranges and the availability of irrigation water. Some regions may experience lower yields or greater crop stress, while others may temporarily gain longer growing seasons. It does not directly change the Moon's distance or mountain height.

Correct answer: A. कई क्षेत्रों में सूखे की आवृत्ति और तीव्रता

Explanation: As Earth warms, evaporation and atmospheric moisture may increase, but rainfall does not change in the same way everywhere. Shifting circulation and uneven precipitation can make some regions drier, increasing the frequency and severity of droughts. Sea ice generally declines, and warming does not change the length of a day.