The correct answer is A] decomposers.
Legumes such as peas and beans have nodules on their roots that contain nitrogen-fixing bacteria Rhizobium which fixes atmospheric nitrogen into ammonium ions which can be used by plants. Plants absorb nitrogen compounds through their roots. When plants die, the nitrogen compounds in the organic matter re-enter the soil by the decomposers. Decomposers breaks down dead organic matter into ammonia, which can then go through the nitrification process.
