Select the correct answer.
What's the role of oxygen in cellular respiration?
A.
It accepts electrons and keeps the electron transport chain running.
B. It breaks down carbon-based sugar molecules to release energy and forms carbon dioxide.
C.
It combines with hydrogen ions in sugar molecules to release energy and form water.
D.
It supplies electrons to the electron transport chain to keep it running.

there's the proffessional site that will you.

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.