Many populations in a specific area or region at a certain time make up a O Community O Niche O Ecosystem O Population

O Community

Explanation:

A community is made up of many populations within a specific area a certain period of time.

i think that d. wind is the answer.   i missed the question when i answered a. currents.

step 1: nitrogen fixation- conversion of atmospheric no₂ into forms useful to plants by lightning, bacteria, and cyanobacteria.

step 2: nitrification-process of converting ammonia to nitrite or nitrate.

step 3: assimilation-plant roots absorb new form of nitrogen.

step 4: ammonification-conversion of organic nitrogen to ammonia by bacteria involved in decomposition.

step 5: denitrification-bacteria turns the decomposed matter back into n₂o, which is released into atmosphere; repeat cycle.