单项选择题
A．change his energy cycle B．overcome his laziness C．get up earlier than usual D．go to bed earlier
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.
A．Nawareness of energy cycles. B．Familiar monologues. C．A change in a family member's energy cycle. D．Attempts to control the energy cycle of other family members.