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since的四种用法(***) 1）since +过去一个时间点（如具体的年、月、日期、钟点、1980, last month, half past six）。例如： I have been here since 1989. 1989起，我一直在这儿。 2）since +一段时间+ ago。例如： I have been here since five months ago. 我在这儿，已经有五个月了。 3）since +从句。例如： Great changes have taken place since you left. 你走后，变化可大了。 Great changes have taken place since we were here. 我们走后，变化可大了。 4）It is +一段时间+ since从句。例如： It is two years since I became a postgraduate student. 我考上研究生有两年了。 历年真题： 1. He has ____ the army for ten years and now is an officer. A.gone into B.joined in C.been in D.come into 答案：C.(其余三组动词均为瞬间动词，不能和段时间连用。) 2. You don't have to describe her. I _____ her several times. A.had met B.have met C.met D.meet 答案：B. 6.现在完成进行时：谓语动词构成：主语 + has/have been doing (一）表示从过去某时开始一直持续到现在的动作，并且还将持续下去。 The Chinese have been making paper for two thousand years. 中国有2000年的造纸历史。（动作还将继续下去） I have been learning English since three years ago. 自从三年前以来我一直在学英语。（动作还将继续下去） (二）表示在说话时刻之前刚刚结束的动作。 We have been waiting for you for half an hour. 我们已经等你半个钟头了。（动作不再继续下去） (三）有些现在完成进行时的句子等同于现在完成时的句子。 They have been living in this city for ten years. They have lived in this city for ten years. 他们在这个城市已经住了10年了。 I have been working here for five years. I have worked here for five years. 我在这里已经工作两年了。 (四）大多数现在完成进行时的句子不等同于现在完成时的句子。 I have been writing a book.（动作还将继续下去） 我一直在写一本书。 I have written a book.（动作已经完成） 我已经写了一本书。 They have been building a bridge. 他们一直在造一座桥。 They have built a bridge. 他们造了一座桥。 (五）表示状态的动词不能用于现在完成进行时。 I have known him for years. 我认识他已经好几年了。 这类不能用于现在完成进行时的动词还有：love爱，like喜欢，hate讨厌，等。 历年真题： I _____ on the door for ten minutes now without an answer. A.was knocking B.am knocking C.knocking D.have been knocking. 答案:D。 因为该句是说到目前为止已经敲了10分钟了，但没人应答。动作一直持续十分钟。因此完成进行时态是最合适的。 7. 过去完成时 1）概念：表示过去的过去 其构成是had +过去分词构成。 2）用法 a.在told, said, knew, heard, thought等动词后的宾语从句。例如： She said （that）she had never been to Paris. 她告诉我她曾去过巴黎。 b.在过去不同时间发生的两个动作中，发生在先，用过去完成时；发生在后，用一般过去时。例如： When the police arrived, the thieves had run away. 警察到达时，小偷们早就跑了。 c.表示意向的动词，如hope, wish, expect, think, intend, mean, suppose等，用过去完成时表示'原本…，未能…'。例如： We had hoped that you would come, but you didn't. 那时我们希望你能来，但是你没有来。 d. 过去完成时的时间状语before, by, until , after, once, as soon as。例如： He said that he had learned some English before. 他说过他以前学过一些英语。 By the time he was twelve, Tom was disappointed that most of the guests had left when he arrived at the party. 汤姆失望了，因为他到达晚会时，大部分客人已经走了。 e.过去完成时常常用在含有：no sooner...Than, hardly/scarcely/barely...When等表示“一。。。就。。。”结构的句子中，句子常考查倒装这种语法项目。 如：I had hardly opened the door when I he hit me. 我刚打开门，他就打了我。 也可表示成：Hardly had I opened the door when I he hit me. 也可表示成：No sooner had he bought the car than he sold it. 典型例题 The students ___ busily when Miss Brown went to get a book she ___ in the office. A. had written, left B.were writing, has left C. had written, had left D. were writing, had left 答案:D.'把书忘在办公室'发生在'去取书'这一过去的动作之前，因此'忘了书'这一动作发生在过去的过去，用过去完成时。句中when表示的是时间的一点，表示在'同学们正忙于……'这一背景下，when所引导的动作发生。因此前一句应用过去进行时。 历年真题： 1. When I went to visit Mrs. Smith last week, I was told she ____ two days before. A.has left B.was leaving C.would leave D.had left 答案：D。 句子意思是：上周当我去看望 2. About the sixth century A.D.when few Europeans could read, the Chinese _____ paper. A.invented B.had invented C.have invented D.had been invented 答案:B。 3. No sooner had we sat down ____ we found it was time to go. A.than B.when C.as D.while 答案:A。 4. The chemistry class ____ for five minutes when we hurried there. A.had been B.was on C.has been on D.would be on 答案：A。
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