Final answer:
The ego adheres to the reality principle, balancing instinctual desires and societal norms, while the id is driven by the pleasure principle seeking immediate satisfaction. The correct option is (b).
Step-by-step explanation:
The ego is to reality, as the id is to pleasure. This statement encapsulates the basic principles in Freudian psychology, where the id is driven by the pleasure principle seeking immediate gratification, while the ego operates on the reality principle, balancing the desires of the id in a realistic way.
The ego's role is to reconcile the demands of the id, which are based on instinctual drives and immediate pleasure, with the moral and societal standards imparted by the superego. Thus, the correct answer to the student's question is option b: reality; pleasure.