Researchers Found That Fish on Coral Reefs That Are Fished

Researchers found that fish on coral reefs that are fished have fewer parasites than fish on coral reefs that exclude fishing. What explains this observation?

A) Fishing eliminated fish with inferior genetics, which were more susceptible to parasites.
B) Fish from unfished reefs had larger populations that made them subject to more transmission of parasites.
C) The unfished site had more parasites than the fished site.
D) none of the above