单项选择题
A．they are too tired to fall asleep B．they are forbidden to sleep at work C．they are kept by treating their patients D．they are too worried about oversleeping
A．can still provide quality medical care B．will remain alert because he is used to it C．may ignore the potential risk of insufficient sleep D．should be fired if he continues the medical operation
A．the longer one sleeps, the less sound sleep he gets B．the more sleep one gets, the more likely a stroke occurs C．many people stick to about eight hours of sleep to stay fine D．many people who sleep six hours a night still feel energetic in the day