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called REM sleep, characterized by rapid eye movements and dreaming, and longer periods of nonREM sleep. 41 Neither kind of sleep is at all wellunderstood , but REM sleep is 42 to serve some restorative(有助于復(fù)元的) function of the brain. The purpose of nonREM sleep is even more 43 .“ 43. A. subtle(狡猾的,敏感的) B. obvious C. mysterious D. doubtful it He was a small man, 43 , and dressed in a clean but old44 suit of clothes…. I was happy with his work, but not happy with the 51 way he worked. He was too quiet. But he worked well: like a 55machine, never looking or speaking. 43. A. silent B. quiet C. excited D. nervous Tautology, namely, repetition, is that some key words or expressions of the same meaning appear in different places to runthrough the whole passage. Tautology is another linking way. For example: 三 . tautology method(復(fù)現(xiàn)法) : chine never 四 . Relevancy method(關(guān)聯(lián)法): Sometimes, two or more words or expressions of the same sort appear as parallel structure (并列結(jié)構(gòu)) at the same time. Generally, one of the parallel is set known, but the other one is unknown. Example: He worked through the day by 48 and into the 49 by candlelight. I was 50 with his work, but not happy with the 51 he worked. Had he been happy and 53 , I would have liked him much better. 48. A. night B. sunlight C. light D. day 49. A. evening B. daylight C. night D. dawn 50. A. happy B. careful C. patient D. satisfy 51. A. manner B. means C. way D. method 53. A. quiet B. humorous C. cheerful D. talkative was happy五 . Time clue(時(shí)間線索) : Example 2: That the introduction of the puter in the early 20th century, 30 by the invention of the integrated circuit(集成電路 ) during the 1960s, radically changed the process” 30. A. brought B. followed C. excited D. charact