单项选择题
A．tire an individual mind B．help infants grow older C．apply pressure on an executive D．depend on an individual age
A．is hard to imagine B．will probably be a mental breakdown C．is difficult to describe D．will probably be dead
A．sleep is important for good mental and physical health B．a light sleep is as restful as a deep sleep C．memory is improved during sleep D．sleep is relatively unimportant for human beings