Which of the following would NOT likely have occurred without the evolution of photosynthetic organisms?

Question

A. Life would be much less diverse.
B. Most organisms would have gone extinct due to the increase in oxygen.
C. Mitochondria-containing cells would not have evolved.
D. There would be no oxygen on Earth.
E. All of the other choices are potential consequences of a photosynthesis-free world.

I believe the answer is A because photosynthetic prokaryotes diversified the ocean; however the wording of the question is confusing me. Thank you for you assistance.