According to Sigmund Freud, girls and boys develop feminine and masculine identities, respectively, when they

A) begin to desire their parent of the opposite sex.
B) relinquish their desire for the other-sex parent and begin to identify with their same-sex parent.
C) begin to express their libido in socially acceptable ways.
D) reach the phallic stage of psychosexual development.

According to Freud's theory of psychosexual development, during the phallic stage (ages 3-6), children begin to develop a sexual identity and become aware of their own gender and those of others. They develop a desire for their opposite-sex parent (the Oedipus complex for boys and the Electra complex for girls) and eventually relinquish this desire in order to identify with their same-sex parents, developing their own gender identity. Therefore, choice B is the correct answer.