Nitrifiers are bacteria
a. capable of living in symbiosis in the roots of some plants.
b. capable of oxidizing NH3 using NO.
c. that convert N2 to NH3.
d. that generate nitrites or nitrates.
e. capable of using NH3 as an electron donor.

(D.) Nitrifiers are bacteria that generate nitrites or nitrates.

Explanation:

In the nitrogen cycle which occurs in nature, ammonia and ammonium compounds in the soil from organic sources and are converted to nitrites and nitrates by aerobic microorganisms.

Nitrifiers, as the name implies, are these such aerobic bacteria which oxidize inorganic constituents in the soil to generate energy. Examples of these nitrifiers are nitrobacter and nitrosomonas.

b.final

it's c (engineer's do their work with mechanical stuff not on any living being)