Answer:

B

Explanation:

Assimilation is the process by which plants and animals incorporate the NO3- and ammonia formed through nitrogen fixation and nitrification. Plants take up these forms of nitrogen through their roots, and incorporate them into plant proteins and nucleic acids. Animals are then able to utilize nitrogen from the plant tissues.

D. FIXATION

Nitrogen fixation is the process by which nitrogen is taken from its molecular form (N2) in the atmosphere and converted into nitrogen compounds useful for other biochemical processes. Fixation can occur through atmospheric (lightning), industrial, or biological processes.