Nitrogen fixation a) is the process where nitrogen is converted to a usable form
b) is accomplished by plants when they break down soil.
c) occurs as a result of photosynthesis
d) none of the above

A. is the process where nitrogen is converted to a usable form

Explanation:

Fixation converts nitrogen in the atmosphere into forms that plants can absorb through their root systems. A small amount of nitrogen can be fixed when lightning provides the energy needed for N2 to react with oxygen, producing nitrogen oxide, NO, and nitrogen dioxide, NO2

the scientific method.

air enters through the nose, moves through the nasal cavity, the pharynx, the larynx, enters the trachea, moves through the bronchi andbronchioles till the alveoli.