Question

The statements that are TRUE : (A) methane leads to both global warming and photochemical smog (B) methane is generated from paddy fields (C) methane is a stronger global warming gas than CO₂ (D) methane is a part of reducing smog. Choose the most appropriate answer from the options given below :

• A. (A) and (B) only
• B. (A), (B), (C) only
• C. (B), (C), (D) only
• D. (A), (B), (D) only

Hint:

Photochemical smog is "oxidizing" in nature (NOx, O₃, hydrocarbons), whereas Classical smog is "reducing" ($SO_2$).

Answer 1

The Correct Option is B

To determine which statements are true about methane, let's evaluate each option carefully:

1. Statement (A): "Methane leads to both global warming and photochemical smog."
   • Global Warming: Methane is a significant greenhouse gas that contributes to global warming. It traps heat in the atmosphere effectively.
   • Photochemical Smog: Methane itself is not a significant direct contributor to photochemical smog. Photochemical smog typically involves volatile organic compounds, nitrogen oxides, and sunlight. However, methane can indirectly contribute by interacting with other chemicals under certain conditions.
   • Conclusion: This statement is partially true, mainly concerning global warming.
2. Statement (B): "Methane is generated from paddy fields."
   • Paddy fields produce methane during the anaerobic decomposition of organic matter in waterlogged soils. This is a well-known source of methane emissions.
   • Conclusion: This statement is true.
3. Statement (C): "Methane is a stronger global warming gas than CO₂."
   • Methane has a much higher global warming potential than carbon dioxide over a 20-year period. Methane is over 20 times more effective at trapping heat in the atmosphere than CO₂ per unit of mass.
   • Conclusion: This statement is true.
4. Statement (D): "Methane is a part of reducing smog."
   • Reducing smog refers to smog formed in the presence of reducing agents like sulfur dioxide, as opposed to oxidizing agents seen in photochemical smog. Methane is not a reducing agent and does not participate in the formation of reducing smog.
   • Conclusion: This statement is false.

Based on this analysis, the statements that are true are (A), (B), and (C).

Therefore, the correct answer is: (A), (B), (C) only