Which process occurs when bacteria converts nitrogen gas to a usable form?

Fixation

Explanation:

Nitrogen is converted from atmospheric nitrogen (N2) into usable forms, such as NO2-, in a process known as fixation. The majority of nitrogen is fixed by bacteria, most of which are symbiotic with plants. Recently fixed ammonia is then converted to biologically useful forms by specialized bacteria.

the correct answer, according to e2020, is the second choice there is an occluded front in region a and a cold front in region b.