Please help me with this question:( Endosymbiotic theory is most useful for explaining the development of which of these organisms?

A prokaryotes that could perform photosynthesis
B. single-celled eukaryotes that could gain energy by combining food with oxygen
d
C. multicellular plants and animals that could live either on land or in the water
.
D. single-celled eukaryotes that kept their DNA in a membrane-bound nucleus