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

Defines 'wet padi cultivation' (rice grown in flooded lowlands) — a distinctive wet, waterlogged practice.

A student can connect flooded/wet soils to anaerobic microbial activity (like in wetlands) that produces CH4, suggesting rice fields are plausible CH4 sources among these crops.

States methane is emitted by natural wetlands and similar sources.

By analogy, flooded rice paddies resemble wetlands; combining this with (3) supports suspecting rice fields emit substantial CH4 compared with dryland crops.

Gives rice's very large global area and central role as a staple crop (about 150 million ha).

Large cultivated area implies a proportionally large potential contribution to any per-area greenhouse-gas emission (CH4 or N2O) relative to crops with smaller area.

Notes heavy irrigation of rice in major producing states and that about one-fourth of cropped area in the country is under rice.

High irrigation/waterlogging prevalence increases the relevance of wet-soil methane processes and also indicates rice's dominance in cropped area locally, informing comparisons with cotton, sugarcane, and wheat.

Explains that human activities including agriculture are increasing atmospheric N2O.

A student could combine this with knowledge that N2O arises from fertilized soils and that rice fields are intensively managed/irrigated to assess whether rice (vs. the other listed crops) likely contributes more N2O per area or in total.