Answer:
In the process of nitrogen fixation, the decomposers convert free nitrogen into ammonia so that it can be used again by the plants in the soil. So the answer is 'A'.
Step-by-step explanation:
Nitrogen fixation is the process by which nitrogen is converted into other organic forms and then broken down again to carry out the cycle again.
All the organisms use a fixed form of nitrogen to produce amino acids. The cycle helps the plants by providing them with ammonium. Nitrogen Fixation is carried out by bacteria, decomposers etc. When the nitrogen is fixed and utilized, the decomposers help in breaking down proteins in the excreta and bodies of dead organisms, converting it back into ammonia for the plants to use. In short, they carry out the recycling process.