Question

what do the nitrogen - fixing bacteria in the soil/roots of plants convert the nitrogen gas to? (select all that apply)
nitrate
nitrite
ammonia
ammonium
rewatch

Explanation:

Nitrogen - fixing bacteria in soil/plant roots convert nitrogen gas ($N_2$) into ammonia ($NH_3$) first. Ammonia can then be further converted into ammonium ($NH_4^+$) in the soil. Nitrate ($NO_3^-$) and nitrite ($NO_2^-$) are produced through nitrification processes by other bacteria, not directly by nitrogen - fixing bacteria.

Answer:

C. Ammonia, D. Ammonium