If a student uses high-energy time for easy tasks and does difficult tasks when tired, what is the main issue?

Correct answer: Weak energy management

Energy management means matching the difficulty and importance of tasks with periods when attention and mental energy are strongest. Placing demanding work in a high-energy period and routine work in a lower-energy period can improve efficiency. The described student is using this resource poorly; the problem is not excess motivation, lack of materials, or high self-esteem. Thus, C is correct.