单项选择题

Thanks in part to technology and its constant sounding and ringing, roughly 41 million people in the United States—nearly a third of all working adults—get six hours or fewer of sleep a night, according to a recent report.
(1) , mention of our ever increasing sleeplessness is followed by calls for earlier bedtimes (2) a longer night’s sleep. But this directive may be (3) of the problem. (4) helping us to get more rest, the tyranny of the eight-hour block (5) a narrow conception of sleep and how we should (6) it. Doctors who peddle sleep aid products and call for more sleep may (7) reinforce the idea that there is something wrong about interrupted sleep (8) . Sleep anxiety is a common result. Some of the time we spend (9) and turning may even result from (10) about sleep and our bodily needs.
Thomas A. Wehr, a psychiatrist (11) at the National Institute of Mental Health in Bethesda, Md., was conducting an experiment in which subjects were deprived of (12) light. Without the illumination and (13) from light bulbs, televisions or computers, the subjects slept (14) the night, at least at first. But, after a while, Dr. Wehr noticed that subjects began to wake up a little after midnight, lie awake for a couple of hours, and then (15) back to sleep again.
It seemed that, (16) a chance to be free of modern life, the body would naturally settle into a (17) sleep schedule. (18) they broke their conception of what form sleep should (19) , they looked forward to the time in the middle of the night as a chance for deep thinking of all kinds, (20) in the form of self-reflection or getting a jump on the next day.