Which of the Following Statements About Reciprocal Altruism Is Most

Which of the following statements about reciprocal altruism is most accurate?

A) Reciprocal altruism is a strictly human phenomenon and observed only in mature adults.
B) Reciprocal altruism is a strictly human phenomenon that has been observed throughout the lifespan.
C) Reciprocal altruism occurs in humans and nonhuman primates but not in nonprimate animals.
D) Reciprocal altruism has been demonstrated in nonhuman primates as well as nonprimate animals.