Which Statement Has Been Proposed as the Reason the Human

Which statement has been proposed as the reason the human brain, in terms of its size, has likely reached a plateau?

A) If the brain were larger, an adult head would be too heavy for the body to carry.
B) The size of a baby's head already puts significant strain on the mother in terms of the difficulties of childbirth.
C) Evolutionary pressures on humans have been removed because humans have already attained control over the environment.
D) None of the above