Nitrogen fixation is the

conversion of gaseous nitrogen into an organism friendly form (ammonia (NH4). preplanned setting of atmospheric levels of nitrogen at 78% stabilizing elemental nitrogen into a gaseous two-atom molecule (N2) the reduction of nitrate (NO3-) to gaseous nitrogen. the repair of D. N. A. by adding nitrogen to the organism's diet

Nitrogen fixation is the conversion of gaseous nitrogen into an organism friendly form (ammonia).

Explanation:

Nitrogen fixation -

It is very important and necessary process by which the nitrogen gas present in the atmosphere gets converted to nitrogen derivatives like ammonia in the soil, is referred to as the process of nitrogen fixation.

This occurs due to the reason, that the derivatives of nitrogen are of much more importance than the molecular nitrogen.

Biologically the process is done by the rhizobium bacteria.

Hence,

From the question,

The correct option is a.