According to psychoanalytic theory, the child's prime focus of pleasure in the first year of life is the .

The mouth

Explanation:

The oral stage of personality is the first stage that children undergo. The stage is concerned with the primary focus of oral gratification. The primary source of interaction for children at this stage is the mouth, hence, oral stimulation such as sucking is common for them at this stage of their development. It usually in the first 18months of their development.