Text 1You might be forgiven for thinking that sleep researchers are a dozy bunch. Most of the other things people do regularly -- eat, excrete, copulate and so on -- are biologically fairly straightforward: there is little mystery about how or why they are done. Sleep, on the other hand, which takes up more of most people’ s time than all of the above, .and which attracts plenty of study, is still fundamentally a mystery.The one view shared by all is that sleep matters. For evidence, look no further than the experiments led by Allan Rechtaschaffen and Bernard Bergmann at the University of Chicago in the 1980s. They kept experimental rats awake around the clock in an environment where control rats were allowed as much sleep as’ they wanted. The sleep - deprived rats all died within a month.Carol Everson worked with the Chicago team as a graduate student and now has a job at the National Institutes of Health in Bethesda, Maryland. While repeating the Chicago experiments she was struck by the fact that, although the sleep - deprived rats showed no obvious symptoms of particular diseases--and no such signs were picked up in post - mortems--their emaciation and generally sorry state was reminiscent of that which befalls many terminal cancer patients and AIDS patients, whose immune systems have packed up. While Dr Everson does not claim to have hard and fast proof that sleep is needed for resistance to infection, her work does point that way-- as does the re search of others around the world.Another approach is to look for chemicals that cause sleep; from these, you should be able to start telling a biological story which will eventually reveal the function of sleep. Peter Shiromani of Harvard Medical School has found a protein that builds up at high levels in chronically sleep - deprived cats, but disappears within an hour if the animals are allowed 45 minutes of recovery sleep. Researchers at the University of Veron have found something similar. But no one chemical tells the whole story.So new ways of inducing sleep may soon be available; an understanding of its purpose, though, remains elusive. In this, sleep is like the other great biological commonplace that is still mysterious: consciousness, which is also easily altered chemically but not too well under stood. No one knows how Consciousness arises, or what , if anything, it is for( though there are a lot of theories). Almost the only thing that can be said about it for certain is that you lose it when you fall asleep. Solving the mystery of sleeping and waking might require new insights into the consciousness that is lost and regained in the process. Putting it this way makes the problem sound rather grander, and the lack of progress so far look a bit less dozy. The experiments led by Allan Rechtaschaffen and Bernard Bergmann at the University of Chicago （）

A. couldn' t prove that sleep matters
B. allowed the control rats as much sleep as possible
C. showed that sleep is still fundamentally mystery
D. kept the experimental rats up all day and all night