【单选题】The normal human daily cycle of activity is of some 7—8 hours' sleep alternation with some 16—17 hours' walness and that the sleep normally coincides 【B1】 the hours of darkness. Our present concer...
【单选题】The normal human daily cycle of activity is of some 7-8 hours' sleep alternating with some 16-17 hours' wal- ness. Broadly speaking, the sleep normally______ with the hours of darkness.