I think it's B: DNA replication
Answer: a. oxygen
Basically what (/the) ETC and oxidative phosphorylation is, is the products of the Krebs cycle being oxidized and oxygen receiving electrons. And when the phosphorylation part of oxidative phosphorylation occurs is when ADP gains its third phosphate group becoming ATP.
Forgive me for this poor response I was trying to be quick and it resulted in this vague and disorganized mess. To properly explain the ETC and oxidative phosphorylation it would be best to start from the beginning and explain all the stages of Aerobic respiration. Then it would be easier to Segway in to this final stage which would definitely take 2-3 descriptive paragraphs to cover.
I believe it is either B or A, personally i'm leaning towards B, but at the same time, i don't think that we would be obtaining materials via pollination, so it then causes A to make more sense.
Produced during ATP synthase in the mitochondria
4. nucleoid region
Bacterial cell's do not have a nucleus; their DNA is found in this region.
