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

Answer: (b) Rice

Flooded paddy has no oxygen, so microbes make methane; heavy nitrogen fertiliser adds nitrous oxide.

The idea

Fixes: alternate wetting and drying, direct-seeded rice (DSR) and neem-coated urea cut both gases.

Flooded paddy → no oxygen in soil → microbes make CH₄ → + N fertiliser → N₂O

Why the others are wrong

(a) Cotton uses fertiliser (N₂O) but grows on dry fields — no methane.

(c) Sugarcane releases some N₂O but is not flooded.

(d) Wheat is grown on dry soil in winter — little methane.

The trap

Wheat and rice are both big fertiliser users, so they look equal. Only rice is FLOODED — that’s where the methane comes from.