Two nutrient solutions are maintained at the same pH. Actively respiring mitochondria are isolated and placed into each of the two solutions. Oxygen gas is bubbled into one solution. The other solution is depleted of available oxygen. Which of the following best explains why ATP production is greater in the tube with oxygen than in the tube without oxygen?

A. The rate of proton pumping across the inner mitochondrial membrane is lower in the sample without oxygen. B. Electron transport is reduced in the absence of a plasma membrane. C. In the absence of oxygen, oxidative phosphorylation produces more ATP than does fermentation. D. In the presence of oxygen, glycolysis produces more ATP than in the absence of oxygen.

Was told the answer is A. but i need help justifying that and why it is not D

Glycolysis is not an oxygen dependent process and the rate of glycolysis is not affected by the amount of oxygen present. The amount of oxygen present affects the rate of oxidative phosphorylation in the mitochondria. Hence with more oxygen present, there is increased oxidative phosphorylation in the presence of high amounts of final electron acceptor O2 which pumps more protons across the membrane and results in a steeper proton gradient across the mitochondrial membrane thus increasing the rate of ATP production. Thus the answer is A as the rate of proton pumping is increased with higher rate of oxidative phosphorylation due to the abundance of final electron acceptor O2.