According to social-role theory, today's gender differences exist because of

The answer is D) Social Pressures

According to the latest social-role theories, every human is a product of their surroundings, upbringing, community and culture.

Hence, gender roles, that most men and women naturally follow, are actually a result external forces and what they told to do.

According to the theory, parents, friends, movies, TV, magazines all project a certain role for each gender and if these external forces were eliminated, most children would grow up to be gender neutral.

According to social role theory, gender differences originate because men and women are distributed differentially into occupational and family roles. Men, for example, are naturally expected to assume the role of a bread winner. Women, on the other hand, are expected play the house wife roles such as cooking. This modus operandi is then learnt by their children as they grow up.