He may act tough, but ______ he is a kind person.

单项选择题If one wants to work more efficiently at his low point in the morning, he should （）

A．change his energy cycle
B．get up earlier than usual
C．overcome his laziness
D．go to bed earlier

单项选择题Which of the following statements is NOT TRUE（）

A．Getting off to work with a minimum effort helps save one's energy.
B．Dr. Kleitman explains why people reach their peaks at different hours of day.
C．Habit helps a person adapt to his own energy cycle.
D．Children have energy cycles, too.