The mere-exposure effect refers to the fact that

A) we tend to dislike someone we are merely exposed to, if we are unable to interact with them.
B) proximity makes people like each other less.
C) we tend to prefer people we have merely been exposed to over those we know well.
D) we tend to increase our liking for people who have become familiar.

The mere-exposure effect, also known as the familiarity principle, refers to the phenomenon where people tend to increase their liking for something or someone with whom they are familiar. Research has shown that repeated exposure to a stimulus, such as a person's face or a product, can lead to more positive evaluations and increased preference for that stimulus, even if there is no meaningful interaction or information about the stimulus. Therefore, D is the correct answer.