Cleaner Wrasse Are Mutualists of Other Coral Reef Fishes

Cleaner wrasse are mutualists of other coral reef fishes. What benefit do they provide to those other fish?

A) They suppress diseases because they consume carcasses of dead fish.
B) They keep water oxygenated because they consume organic debris before it can rot.
C) They keep fish relatively free of externally feeding parasites.
D) They maintain fish habitat by keeping corals free of encrusting algae.
E) They reduce fish mortality by repelling large vertebrate predators.