Free Environment and Atmosphere MCQs with Answers

231. The main culprit of greenhouse effect is Carbon dioxide. But which is the second element contributing most to greenhouse effect

• A. Nitrogen Dioxide (NO2)
• B. Chlorofluorocarbons (CFCs)
• C. Methane (CH4)
• D. High-fructose corn syrup (HFCs)

Explanation: Among the listed gases, methane is generally identified as the second-largest contributor to human-caused greenhouse warming after carbon dioxide. CFCs are extremely powerful per molecule but occur in much smaller amounts.

232. As a result of which treaty, ozone hole in Antarctica is slowly healing?

• A. Koyoto protocol
• B. Ottawa treaty
• C. Montreal protocol
• D. Oslo Accord

Explanation: The Montreal Protocol controls ozone-depleting chemicals such as CFCs, allowing stratospheric ozone to recover gradually. The Kyoto Protocol mainly addressed greenhouse-gas emissions.

233. Montreal Protocol 1987 was__________?

• A. Treaty among nations to reduce nuclear arsenals
• B. Climate control treaty
• C. Treaty to protect ozone layer
• D. Trade policy about tarrifs

Explanation: The 1987 Montreal Protocol is an international agreement to phase out substances that destroy the ozone layer, especially CFCs. It is not a nuclear-arms or tariff treaty.

234. Disolved oxygen (DO) in water should be?

• A. 400 to 800 ppm
• B. 4000 to 8000 ppm
• C. 0.4 to 0.5 ppm
• D. 4 to 5 ppm

Explanation: Dissolved oxygen in reasonably healthy water is commonly around 4 to 5 ppm or higher, with cold, clean water holding more oxygen. The hundreds or thousands of ppm options are far too high for ordinary water.

235. Why normal rain is slightly acidic?

• A. due to presence of dust in air
• B. carbon dioxide and water in clouds react to form carbonic acid
• C. Ozone depletion
• D. All of these

Explanation: Rain absorbs atmospheric carbon dioxide, forming weak carbonic acid and giving normal rain a mildly acidic pH. Ozone depletion and dust are not the basic chemical cause of ordinary rain's acidity.

236. The yellow colour in photochemical smog is due to the presence of____________?

• A. Sulphur dioxide
• B. Carbon dioxide
• C. Nitrogen dioxide
• D. CFC's

Explanation: Nitrogen dioxide gives photochemical smog its characteristic yellow-brown colour and is produced largely by vehicle combustion. Sulphur dioxide is associated more with industrial pollution and acid rain.

237. "Ornithology" is the study of_____________?

• A. Birds
• B. Insects
• C. Sea Plants
• D. Sea Animals

Explanation: Ornithology is the branch of zoology concerned with birds, including their classification, behaviour and distribution. The study of insects is entomology.

238. Wind always blows from area of ________?

• A. Low pressure to high pressure
• B. High pressure to low pressure
• C. Only low pressure
• D. Only high pressure

Explanation: Air moves because of pressure differences, generally flowing from regions of high pressure toward regions of low pressure. Unequal heating of Earth's surface creates many of these differences.

239. The density of Air is_____________?

• A. 0.225 kg/m3
• B. 1.025 kg/m3
• C. 1.225 kg/m3
• D. 1.425 kg/m3

Explanation: At about sea level and room temperature, dry air has a density near 1.225 kg/m³. Its density changes with temperature, pressure and humidity.

240. The hard, solid rocks, whose composition or texture has been changed by heat or pressure in the Earth are called____________?

• A. Sedimentary rocks
• B. Metamorphic rocks
• C. Igneous rocks
• D. All of the above

Explanation: Metamorphic rocks form when existing rocks are altered by heat, pressure or chemically active fluids without completely melting. Sedimentary rocks form from deposited material, while igneous rocks solidify from molten rock.