Question

what is the role of bacteria in the nitrogen cycle? they convert nitrogen gas into ammonia they release nitrogen gas into the atmosphere they convert ammonia into carbon dioxide they absorb nitrogen from the soil

Explanation:

In the nitrogen - cycle, nitrogen - fixing bacteria convert atmospheric nitrogen gas ($N_2$) into ammonia ($NH_3$) through nitrogen fixation. This makes nitrogen available for plants and other organisms in a usable form. The other options are incorrect as bacteria do not release nitrogen gas into the atmosphere in the context of making it available in the cycle (they can denitrify but that's not the main role asked), they don't convert ammonia into carbon dioxide, and they don't absorb nitrogen from the soil in the way described for the nitrogen - cycle role.

Answer:

They convert nitrogen gas into ammonia