Which of the Following Is a Major Evolutionary Step That

Multiple Choice

Which of the following is a major evolutionary step that is hypothesized to have occurred in the evolution of photosynthesis?

A) the acquisition by cyanobacteria of a second photosystem.
B) the ability to use water as an electron donor
C) the acquisition by eukaryotic organisms of photosynthesis by endosymbiosis
D) All three of these steps are hypothesized to have been important in the evolution of photosynthesis.