Questions: George Vaillant developed the Vaillant's Theory of Adult Development.

The answer is Adult Development.

Explanation for each option:

1. Adult: This is the correct answer. George Vaillant is known for his work on adult development, particularly through his longitudinal studies on adult life and aging. His theory focuses on the stages and adaptive mechanisms that individuals use throughout their adult lives.

2. Social: This is incorrect. While Vaillant's work does consider social factors as part of adult development, his primary focus is on the stages of adult development rather than social development specifically.

3. Human: This is incorrect. "Human development" is a broad term that encompasses all stages of life, from infancy to old age. Vaillant's theory specifically addresses the adult phase of human development.

4. Child: This is incorrect. Vaillant's theory does not focus on child development. Instead, it is centered on the stages and adaptive mechanisms in adult life.

George Vaillant's contributions to psychology are significant in understanding how adults adapt and grow throughout their lives, emphasizing the importance of positive psychological development and resilience.