How does Oxygen go through physical changes?

Explanation:

The oxygen molecules move, by diffusion, out of the capillaries and into the body cells. While oxygen moves from the capillaries and into body cells, carbon dioxide moves from the cells into the capillaries. Carbon dioxide is brought, through the blood, back to the heart and then to the lungs

the answer to your question is b

step 1: nitrogen fixation- conversion of atmospheric no₂ into forms useful to plants by lightning, bacteria, and cyanobacteria.

step 2: nitrification-process of converting ammonia to nitrite or nitrate.

step 3: assimilation-plant roots absorb new form of nitrogen.

step 4: ammonification-conversion of organic nitrogen to ammonia by bacteria involved in decomposition.

step 5: denitrification-bacteria turns the decomposed matter back into n₂o, which is released into atmosphere; repeat cycle.