Some Large Fish Allow Smaller Fish to Swim Inside of Their

Multiple Choice

Some large fish allow smaller fish to swim inside of their mouths without eating the smaller ones. The smaller fish get food for themselves from the larger fish's mouth and at the same time remove parasites from its teeth. This is an example of

A) reciprocal altruism.
B) kin selection.
C) audience inhibition.
D) the cost-reward model.