Among the following crops, which one is the most important anthropogenic source of both methane and nitrous oxide?

• (a) Cotton: Cotton is not a major source of methane; nitrous oxide may arise from fertilizer use, but it is not the most important source of both gases. Verdict: Incorrect.
• (b) Rice: Flooded paddy fields create anaerobic conditions that emit methane, and nitrogen fertilizers used in rice cultivation also generate nitrous oxide. Verdict: Correct.
• (c) Sugarcane: Sugarcane can involve fertilizer-related nitrous oxide emissions, but it is not a major methane-emitting crop like paddy. Verdict: Incorrect.
• (d) Wheat: Wheat fields are associated more with nitrous oxide from fertilizers, not significant methane emissions. Verdict: Incorrect.

Answer: (b) Rice.