Final answer:
The preeminent psychosocial accomplishment between the ages of 2 and 6 is learning when and how to regulate emotions.
Step-by-step explanation:
The preeminent psychosocial accomplishment between the ages of 2 and 6 is learning when and how to: C) Regulate emotions. During the early childhood years, children undergo significant psychosocial development, and the mastery of emotional regulation stands out as a crucial accomplishment. This period is characterized by rapid cognitive, social, and emotional growth. Learning to regulate emotions involves understanding and managing one's feelings, expressing emotions appropriately, and developing coping mechanisms. The ability to regulate emotions lays the foundation for effective social interactions, problem-solving, and overall emotional well-being. It contributes to successful relationships, academic achievement, and the development of key social skills that are vital throughout one's life.