Final answer:
During the phallic stage, a major event is the development of the Oedipus complex in boys and the Electra complex in girls, which contributes to the formation of the superego. The correct option a.
Step-by-step explanation:
A major event that occurs during the phallic stage of Freud's psychosexual stages of development is the development of the Oedipus complex in boys and the corresponding Electra complex in girls. The phallic stage is characterized by children's discovery of a primary source of pleasure and their emerging identity.
Boys develop the Oedipus complex, which involves a desire for their mother and jealousy towards their father, often leading to fear of punishment, known as castration anxiety. The conflict is thought to be resolved when the boy identifies with his father, which then aids in the development of the superego. For girls, the analogous concept is the Electra complex, whereby a daughter feels a rivalry with her mother for her father's attention.