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Sleep is divided into periods of so-called REM sleep, characterized by rapid eye movements and dreaming, and longer periods of non-REM sleep. 41 kind of sleep is at all well-understood , but REM sleep is 42 to serve some restorative function of the brain. The purpose of non-REM sleep is even more 43 .The new experiments, such as these 44 for the first time at a recent meeting of the Society for Sleep Research in Minneapolis, suggest fascinating explanations 45 of non-REM sleep .
For example, it has long been known that total sleep 46 is 1OO percent fatal to rats, yet ,47 exanlination of the dead bodies , the animals look completely normal . A researcher has now 48 the mystery of why the aninlals die. The rats 49 bacterial infections of the blood ,50 their immune systems--the self-protecting mechanism against disease--had crashed.
| 41 . |
(A)Either |
(B)Other |
(C)Each |
(D)Any |
| 42 . |
(A) intended |
( B)required |
(C) assumed |
(D) inferred |
| 43 . |
(A) subtle |
(B)obvious |
(C)mysterious |
(D)doubtful |
| 44 . |
(A) maintained |
(B) described |
(C)settled |
(D)afforded |
| 45. |
(A)in the light |
(B)by virtue |
(C)with the exception |
(D)for the purpose |
| 46 . |
(A) reduction |
(B) destruction |
(C) deprivation |
(D) restriction |
| 47. |
(A)upon |
(B)by |
(C)through |
(D)with |
| 48. |
(A)paid attention to |
(B)caught sight of |
(C)laid emphasis on |
(D)cast light on |
| 49 . |
(A) develop |
(B)produce |
(C)stimulate |
(D)induce |
| 50. |
(A)if |
(B)as if |
(C)only if |
(D)if only |
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