By what process does nitrogen enter the living components of ecosystems?

The second process of the nitrogen cycle after nitrogen fixation in the atmosphere. Nitrogen enters the living components through a process called nitrogen assimilation. This is the absorption of nitrite ions in plants roots or through digestion of plants enriched with nitrogen. 

The answer is 0.01 meter

Ithink the answer is c. i’m not sure though i’ll notify you when i have an exact answer!