Final answer:
The child's self-concept most improved by completing a musical performance well is the child who values the activity highly. Success in important areas leads to pride and accomplishment according to Erikson's psychosocial development stages. Support from parents and teachers is crucial for fostering a child's self-concept.
Step-by-step explanation:
The child's self-concept that is boosted most by demonstrating high competence in musical performance is d. A child who thinks musical performance is very important. When children value an activity and are able to demonstrate competence in it, it tends to significantly bolster their self-esteem and sense of self-worth. According to Erikson's theory of psychosocial development, during the elementary school stage, children are in the midst of developing a sense of industry versus inferiority. This means they are comparing themselves to peers and are keenly aware of their abilities and successes. Success in an area that they consider important can lead to a strong sense of pride and accomplishment. In contrast, for a child who does not value the activity or one who already demonstrates natural competence, the boost in self-concept may not be as significant because their sense of self-worth is less tied to that particular achievement or it is expected.
Parents and teachers can foster a sense of competence by providing opportunities to succeed, offering encouragement, valuing effort over innate ability, and helping children set achievable goals. Encouraging participation in activities that the child values, such as musical performance, can be particularly effective in promoting a positive self-concept.