The correct answer is (b), rice. Rice is the most important anthropogenic source of both methane and nitrous oxide. Methane is a greenhouse gas that is 25 times more potent than carbon dioxide, while nitrous oxide is a greenhouse gas that is 300 times more potent than carbon dioxide. Both methane and nitrous oxide are released into the atmosphere from rice cultivation through a variety of processes, including the production of rice straw, the application of fertilizer, and the flooding of rice paddies.
Cotton (a) is a major source of methane, but not nitrous oxide. Sugarcane (c) is a major source of nitrous oxide, but not methane. Wheat (d) is a major source of neither methane nor nitrous oxide.
Here is a more detailed explanation of each option:
- Cotton is a major source of methane, but not nitrous oxide. Methane is released from cotton cultivation through a variety of processes, including the production of cotton linters, the application of fertilizer, and the irrigation of cotton fields.
- Sugarcane is a major source of nitrous oxide, but not methane. Nitrous oxide is released from sugarcane cultivation through a variety of processes, including the production of sugarcane bagasse, the application of fertilizer, and the burning of sugarcane fields.
- Wheat is a major source of neither methane nor nitrous oxide. Methane and nitrous oxide are not released from wheat cultivation in significant amounts.
- Rice is the most important anthropogenic source of both methane and nitrous oxide. Methane is released from rice cultivation through a variety of processes, including the production of rice straw, the application of fertilizer, and the flooding of rice paddies. Nitrous oxide is released from rice cultivation through a variety of processes, including the production of rice straw, the application of fertilizer, and the flooding of rice paddies.