Concept:Legumes form a mutualistic association with nitrogen-fixing bacteria that convert inert atmospheric nitrogen into a usable form.
Explanation:The bacterium
Rhizobium resides in the root nodules of leguminous plants.
In this symbiotic relationship, the plant provides carbohydrates and shelter, while the bacterium supplies fixed nitrogen.
Rhizobium converts free atmospheric nitrogen gas (
N2) into ammonia (
NH3).
This process is known as biological nitrogen fixation.
The ammonia is then used by the plant to synthesize amino acids and proteins.
Therefore, the conversion is from nitrogen gas to ammonia, not from nitrates or nitrites.
Answer:C. nitrogen gas to ammonia