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飘香哈达 - 2008-6-15 7:44:00

第一个用法，也就是在GMAT中常出现的 - 用在indirect speech （report speech）- 也就是说信息提供的人不是直接的陈述者。如human beings are thought to have first entered the Americans 大全325题human beings first entered这个观点不是这篇文章的作者这么想，而是 are thought（被认为 – 被人们认为）
因为to have 是用在indirect speech，所以经常跟在think, claim, believe 等于陈述信息相关的单词后面多以被动的形式出现. To 前面动词的事态没有限制
可以从以下的例子中仔细体会 – 例子是从CD 的贴子中借的，都是大全例的例子
it is thought to have happened
six teenagers claimed to have had vision of the virgin
it is believed to have been the largest
few people are known to have recovered
thought by some scholars to have occurred
alleged to have been worn
经典的例子是大全157题，同时包括 to have 和 to be
Balzac drank more than fifty cups of coffee a day and died of caffeine poisoning; furthermore, caffeine did not seem to bother Samuel Johnson, the great writer and lexicographer, who was reported to have drunk twenty-five cups of tea at one sitting.
(A) furthermore, caffeine did not seem to bother
(B) however, caffeine did not seem to bother
(C) however, caffeine did not seem to have bothered
(D) furthermore, caffeine did not seem to have bothered（B）
(E) in addition, caffeine did not seem to bother
做这个题的时候有些朋友可能看到没有划线部分的have drunk 后根据平行原则选C，但这里因为seem 不是表达别人意见的词，而是做着对这件事情的看法，所以就没有必要用to have bothered 正确答案是B. 如果我们把句子改称
however, it is said caffeine did not to have bothered 这样就可以了
而没有划线部分who was reported to have drunk twenty-five cups of tea at one sitting注意一下这里的was reported 也就是 drunk twenty-five cups of tea at one sitting 这个表述不是作者直接的而是引用别人的report 的所以用了to have 这个形式
第二种用法是future
he is to have become the next president by the end of January
- he will have become the next 与这个意思想象，不过 will 是uncertain is to have 是certain
he was to have been next president (在过去的时点上看未来)
还有现在完成式和过去完成式的用法简单地补充一下
大家都知道现在完成式是跟time 有关，time 对是用现在完成式还是用一般过去式的一个基准。如果有明确的时间或标志词例如，since 等比较好判断，但句子里没有明显的提示时应该怎么判断呢？另外的一半的判断基准是作者是否对他所表达的东西的态度 – 是一般的陈述还是强调。如果是一般的陈述那就用一般过去时，如果作者对描述的东西的态度是强调那就用现在完成式 FOR EXAMPLE
I didn’t eat lunch. I am not hungry 只是一般的陈述
I haven’t eaten lunch, so I am hungry 这里的前面的部分时后面句子的原因，为了表达后面的这个结果必须强调没有吃午饭的这件事情。
GMAT的现在完成式大多符合这个规律
如果那位朋友对现在完成是和一般过去式不太好把握的时候，哪这个基准去判断一下，基本上都很清楚。
一个小tip ： 在打开大全后（word 版面）点击上面编辑 - 查找然后输入关键词 have 就可以不费力气找到所有的根现在完成时有关的题了，复习的时候有效地用这个查找功能有很大的帮助，可以让你很轻松地找到某一个类型来复习。例如复习比较就可以输入 than , as, rather than 等。
过去完成式是从根本上说就是在过去的时点上用一般现在时，也就是把现在完成时搬到过去的时点了
举例大全332题
His studies of ice-polished rocks in his Alpine homeland, far outside the range of present-day glaciers, led Louis Agassiz in 1837 to propose the concept of an age in which great ice sheets had existed in now currently temperate areas.
(A) in which great ice sheets had existed in now currently temperate areas
(B) in which great ice sheets existed in what are now temperate areas
(C) when great ice sheets existed where there were areas now temperate
(D) when great ice sheets had existed in current temperate areas（B）
(E) when great ice sheets existed in areas now that are temperate
我记得很多老师讲过去完成式的时候说这个时态用在一个过去的事情发生在另一个过去的事情以前的时候用，按照此理容易选A 因为
His studies led great ice sheets had existed
这里的led 和 1837 表明这个propose 发生在过去（只不过这里因为式不定式的缘故看不大出来）
那么 ice sheets existed 是这个以前的事情是否也应该用had existed 呢
然而，按照上面的我提过的方法 - 过去的时点上用一般现在时 – 来看如果我们假设我们在1837年的时点上看这个问题那么就会是
Agassiz propose the concept of an age in which great ice sheets existed in now currently temperate area 因为这里是一个对ice sheets存在的一般陈述，而不是强调，所以不必要用
have existed 如果是 have existed的话，那么回到现在的时点看的时候就应该是
led Louis Agassiz in 1837 to propose the concept of an age in which great ice sheets had existed in now currently temperate areas.
而因为就用过去的时点看正确的也是 sheets existed 所以回到现在也是用一般过去时
可能有点罗嗦，总而言之一句话，也就是把现在完成时搬到过去的时点了。其实从另外一个角度也可以理解- 陈述的两件事情没有直接的联系就没有什么内在联系如强调等，那么也没有必要用过去完成式了
例外：大全99
1. Although the manager agreed to a more flexible work schedule, he said that it must be posted on the bulletin board so that both management and labor will know what everyone is assigned to do.
(A) he said that it must be posted on the bulletin board so that both management and labor will know what everyone is
(B) he said it had to be posted on the bulletin board so that both management and labor knows what everyone is
(C) he said that they would have to post the assignments on the bulletin board so that management and labor knew what everyone was
(D) he said that the schedule would have to be posted on the bulletin board so that both management and labor would know what everyone was（A）
(E) saying that the schedule had to be posted on the bulletin board so that both management and labor would know what everyone had been
said that 后面不用按照indirect speech的规律尽管said 是过去式，但后面可以跟现在时我想可能是原话引用的意思吧我记得还有一道类似的题。

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