What Do Evolutionary Psychologists Suggest Is the Reason for Different

What do evolutionary psychologists suggest is the reason for different genders?

A) Different genders result from observing different expectations about gender in our society.
B) Different genders arise because offspring are more likely to survive with two distinct gender roles in place.
C) Different genders arise because of differences in the workplace roles for different people.
D) Different genders arise because we need eggs and sperm to procreate.