primates who live in a group with nonrelatives will engage in altruistic behaviors more often than primates who live with relatives.

the answer is "a.) well–developed vascular system."

explanation:

sorry to break it to ya but no one can answer your question it's just

jk but i am serious about the part that most people cant answer it beacuse you did not mention the section you are talking about. but it would if you added some detail and were a bit more specific.