Which of the following statements is an explanation?

a. aggressive chimpanzees should be monitored during meal times or fed separately from other chimpanzees.
b. chimpanzees will behave aggressively when they feel threatened by other individuals.
c. a chimpanzee associates food stealing with aggression due to evolutionary pressure.
d. giving better supplies of food to chimpanzees will decrease their aggressive behavior.

The correct answer is option C. A chimpanzee associates food stealing with aggression due to evolutionary pressure.

In an experiment, the explanation is the part, which explains the phenomena and its reason for occurrence. In chimpanzees, the aggression is seen because of competition, which is a type of evolutionary pressure. The food stealing is the phenomena, which is commonly observed among chimpanzees. Hence, the statement,  A chimpanzee associates food stealing with aggression due to evolutionary pressure is an explanation, which describes the cause of stealing food with aggression.