Final answer:
The statement that the self is constantly changing and dynamic is true, as supported by psychological and sociological theories.
Step-by-step explanation:
Among the given statements about the self, the most accurate is A. The self is constantly changing and dynamic. Psychological theories, such as those proposed by Erik Erikson and Albert Bandura, as well as sociological perspectives like George Herbert Mead's, suggest that the formation of the self is an ongoing process shaped by social interactions and personal experiences throughout an individual's life. The notion that the self is set in childhood (C) and cannot change, or that it is just a passive absorption of influences (D) contradicts these theories, which highlight the importance of socialization and experiences in shaping one's sense of self. Furthermore, while social experiences contribute to our sense of self, it is incorrect to claim that the self is merely the sum of these experiences (B), as the cognitive processes, behavior, and context also significantly influence self-development.