Question

what converts nitrogen into a usable substance during the nitrogen cycle?
decomposers
consumers
nitrogen - fixing bacteria
legumes

Explanation:

Nitrogen - fixing bacteria play a crucial role in the nitrogen cycle. They convert atmospheric nitrogen (\(N_2\)) into ammonia (\(NH_3\)) through a process called nitrogen fixation. This ammonia can then be further converted into nitrates (\(NO_3^-\)) which are usable by plants. Decomposers break down organic matter, consumers obtain nitrogen by eating other organisms, and legumes are plants that often have a symbiotic relationship with nitrogen - fixing bacteria but do not themselves convert nitrogen in the way described.

Answer:

nitrogen - fixing bacteria