Why Does Sexual Competition Appear to Be Higher Among Humans

Why does sexual competition appear to be higher among humans than other primates?

A) Unlike most other primates, human females are sexually receptive throughout the year.
B) Humans are more likely than other primates to live in multi-male, multi-female social groups.
C) Humans are particularly aggressive primates and more likely to compete through physical means.
D) There is a lower female to male ratio in human communities than in most other primate groups.