Correct Answer: B

Orem's Self-Care Deficit Nursing Theory is a grand theory comprising three nested theories:

1. Theory of Self-Care: Describes why and how people care for themselves (self-care requisites: universal, developmental, health deviation)
2. Theory of Self-Care Deficit: Describes when nursing is needed — when a person's self-care agency is insufficient to meet their therapeutic self-care demand
3. Theory of Nursing Systems: Describes nurse-patient relationships and actions (wholly compensatory, partly compensatory, supportive-educative systems)

The key equation in Orem's theory:
\[\text{Self-Care Deficit} = \text{Therapeutic Self-Care Demand} > \text{Self-Care Agency}\]