人教版高中英语配套ppt课件：选修9 unit 2 period 1精选.pptVIP

【完成句子】 ①Last December，car production went down 24 percent________ ________(相比) the corresponding period of 1972. ②The teacher________ ________ ________(比较和对比) the two poems. ③Books are often________ ________(比作) friends. 答案　①compared with　②compared and contrasted ③compared to 1．We may well wonder how seamen explored the oceans before latitude and longitude made it possible to plot a ships position on a map.我们很可能感到奇怪，在经纬度被用来在地图上标出船只位置之前，海员是如何对海洋进行探索的。 句中 before 引导时间状语从句，意为“在……之前，还没有”。其中made后的it为形式宾语，真正宾语为动词不定式 to plot a ships position on a map。 before 作连词时，可引导时间状语从句，用法如下： (1) 与情态动词 can/could 连用，意为“还未来得及……就……”。 Before I could get in a word， he had measured me. 我还没来得及插话，他就为我量好了尺寸。 (2)才…… We had sailed four days and four nights before we saw land. 我们航行了四天四夜才看到陆地。 【归纳拓展】 (3)不到……就 We hadn‘t run a mile before he felt tired. 我们跑了还不到一英里他就累了。 (4)hardly/scarcely...before...一……就…… We had scarcely reached the school before/when the bell rang. 我们刚到学校铃就响了。 (5)It＋be＋时间段＋before 从句，要过多久才…… 用不了多久就……。 It will be two weeks before everything returns to normal. 两周之后一切才恢复正常。 It wont be long before we meet again. 用不了多久我们就会再见面的。 【单项填空】 The girl had hardly rung the bell________the door was opened suddenly, and her friend rushed out to greet her. A．before B．until C．as D．since 解析　句意：这个女孩刚一按门铃，门就突然开了，她的朋友冲出去迎接她。 before 在……之前，还没有……； until 直到……才；as 当……时候； since 自从……以来。根据句意选A项。题干中 hardly...before...实际上为一固定句式，意思是“刚……就……”，相当于 hardly... when...。 答案　A 2．This seems to have been the first and most useful form of exploration which carried the minimum amount of risk.这似乎已是最早的、最有用的探险方式，所冒的风险也是最小的。 seem后接不定式的完成时，表示该动作发生在seem之前。 He seems to have lost confidence in himself. 他似乎已失去了自信。 They dont seem to have grasped what I meant. 他们好像还没明白我的意思。 He seems to have studied abroad. 他好像在国外学习过。 to have done为不定式的完成时，表示曾经发生的动作或事件。常见的不定式完成时的结构有： be happy to have done be pleased to have done be sorry to have done很遗憾做过…… happen/seem/appear to have done刚好/好像/似乎做过…… consider sb to ha