Researchers Have Found That on Coral Reefs Where Fishing Occurs

Researchers have found that on coral reefs where fishing occurs, the fish have fewer parasites than fish on coral reefs where fishing is excluded. What explains this observation?

A) Fishing eliminated fish with inferior genetics, which were more susceptible to parasites.
B) On coral reefs that excluded fishing, larger populations of fish made them subject to more transmission of parasites.
C) The sites where fishing was excluded had more parasites than the sites with fishing.
D) Fishing removed the largest fish and the largest fish had the most parasites.