Final answer:
Noah is using self-concept by comparing his math and spelling abilities to his peers. Self-concept involves awareness of one's own skills and is crucial for positive development.
Step-by-step explanation:
Nine-year-old Noah is using B. Self-concept when he observes that he is better than his peers at math but not as good at spelling. Self-concept is developed through making comparisons with peers and reflecting on one's abilities and attributes. It is important for parents and teachers to support children in forming a positive self-concept by recognizing their individual strengths and providing encouragement, especially as children compare themselves to others and develop a sense of competence in their abilities during the elementary school stage.