单选题

A Rest frequently during the day.

B Lack of sleep on weekends.

C Lack of exercise in the evening.

D Eating cheese before going to bed.

解析：
[考点]细节题。会导致睡眠问题有几个方面，像一天之内频繁地休息，不锻炼或者晚上大量锻炼，周末睡得很多还很晚。