If You Were Writing a Paper on the Beneficial Aspects

If you were writing a paper on the beneficial aspects of the protists for humans and the environment,which of the following would be excluded from your paper?

A) They have a parasitic relationship with some organisms
B) They can give off oxygen
C) They can be a major component of plankton
D) They can form symbiotic relationships with corals
E) They serve as a food source for many organisms