Final answer:
According to Freud, a three-year-old boy who rejects his father and prefers his mother is experiencing the Oedipus complex, which is part of the phallic stage of psychosexual development.
Step-by-step explanation:
The three-year-old boy's behavior of rejecting his father and only wanting to be with his mother suggests he is going through the Oedipus complex, which is associated with Freud's phallic stage of psychosexual development.
This stage occurs between the ages of 3 and 6 when a child's pleasure-seeking urges are concentrated on the genitals.
The Oedipus complex involves a boy's desire for his mother and the urge to replace his father, who is seen as a rival.
This is often accompanied by castration anxiety and is resolved when the boy starts to identify with his father, thereby relinquishing his romantic feelings for his mother.