The majority of old people have no interest in, nor capacity for, sexual relations.

Which of the following theories explains gender role differences among new parents by saying that men and women function as a couple to swap goods and services?

a. the parental investment theory b. the parental imperative theory c. economic exchange theory d. social role theory.

The function of the pupil is to

A) control the amount of light that enters the eye. B) control eye movements as one tracks a moving object. C) focus light onto the retina. D) invert the visual image on the retina. E) amplify the intensity of light that is passed through the vitreous humor.