时态
1、常用时态的形式：(以动词“study”为例）
时间：现在 过去 将来 过去将来
状态
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一般 study studied shall/will study should /would study
studies
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进行 am/is/are was/were shall/will be should/would be
studying studying studying studying
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完成 has/have had shall/will should/would
studied studied have studied have studied
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完成 has/have had been shall/will should/would
进行 been studying studying have been studying have been studying
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2、理解上表的要点：
1）、过去将来：表示过去某时看来将要发生的动作或情况。
2）、完成时与完成进行时的区别：完成进行时比完成时更强调动作的延续性。
E：He has been watching TV for three hours (强调他还要看下去）
He has been watched TV for three hours（不一定要看下去了）
3、某些时态的不同表示方式：
1）、表示将来发生的动作或情况的几种形式：
a. shll/will +动词原形
b. be going to do sth 常用来表示最近打算要做的事情或即将发生的事
c. be to do sth 表示按计划安排要做的事或要发生的事
d. be about to do sth 表示正要或即将要做的事
2）、现在完成时
a. 表示动作在过去某时发生并已经完成，且对现在有影响。常和以下时间状语连用：already / yet / before / recently / lately / often / rarely /once 等
E：The issue of "mercy killing"has recently boiled over into a fiere public debate in Europe
b. 表示动作始于过去，持续到现在，可能不将持续下去。常和表示一段时间的状语连用：for some time , for three years, since, so far , in the past few years, all this while.
E：During the past few years,the public has focued on AIDS.
c. 可以用在时间状语或条件状语丛句中，表示将来业已完成的动作。
E：We'll start at five o'clock if it has stopped snowing by then.
3）、注意点：现在完成时常用于下列句型：
a. It's/it will be the first /second ……time/day that……
b.This /That is the +形容词最高级
E1：It's the first time I have been to ShangHai
E2：This is the second letter I've written to you this year
E3：It's one of the most interesting books I have ever read
现在完成时不能与表示确定的过去时间连用：yesterday,in 2001,a few year ago等，这些状语一般只用在一般过去时。
