Which are forms of nitrogen that are unsable by humans

Ammonia, nitrates , nitrites

The forms of nitrogen that are unusable by us humans are the gaseous forms of N2 as they can't be used by most living things.

The forms of nitrogen that are usable by us humans are Ammonia, Nitrates, and Nitrites.

significant amounts of nitrogen oxides, carbon monoxide, and other pollution

explanation:

passenger vehicles are a major pollution contributor, producing significant amounts of nitrogen oxides, carbon monoxide, and other pollution. in 2013, transportation contributed more than half of the carbon monoxide and nitrogen oxides, and almost a quarter of the hydrocarbons emitted into our air.

c. is the correct answer