动词时态

　　1)现在完成进行时态 (have/has been + -ing 分词构成): 动作或状态从过去某时开始,继续到现在,可能继续下去,也可能刚刚结束.

　　I’ve been writing letters for an hour.

　　I’ve been sitting in the garden.

　　2)过去完成进行时(由had been + ing分词构成): 过去某个时刻以前一直在进行的动作

　　I’d been working for some time when he called.

　　We had been waiting for her for two hours by the time she came.

　　3)将来完成进行时: 将来某个时刻以前一直在进行的动作.

　　By next summer, he will have been working here for twenty years.

　　In another month’s time she’ll have been studying here for three years.

　　4)将来完成时(由shall/will have + 过去分词构成): 将来某时会业已发生的事.

　　I shall have finished this one before lunch.

　　They’ll have hit the year’s target by the end of October.

　　常考知识点讲解：定语从句引导词

　　that, who, whom: 非限制性定语从句, 如果修饰人, 一般用who, 有时用that (作主语时用who较多). 如果关系代词在从句中作宾语, 就应当用宾格 whom 或that, 但在大多数情况下都可以省略掉, 在口语中可用who代替whom.

　　Here is the man (whom) you’ve been looking for.

　　He is a man (that) you can safely depend on.

　　The people (who/that) you were talking to were Swedes.

　　There are some people here who I want you to meet.

　　但在介词后只能用whom:

　　This is the man to whom I referred.

　　但在口语中一般都把介词放到句子后面去, 这时可用that, 但省略时更多一些.

　　Have you met the person about whom he was speaking?

　　Have you met the person (that) he was speaking about

　　The girl to whom I spoke is my cousin.

　　The girl (who/that) I spoke to is my cousin.

　　限制性定语从句如果修饰“物”, 用关系代词that的时候较多, 也有时用which.. 当这个代词在从句中是用作宾语时, 在绝大多数情况下都是省略的, 特别是口语中(尤其是当被修饰的词是all, everything等词时):

　　Have you everything you need?

　　(Is there) anything I can do for you?

　　All you have to do is to press the button.

　　在介词后只能用which, 在口语中一般都把介词放到从句后部去, 这时可以用that, 但省略的时候更多一些:

　　The tool with which he is working is called a wrench.

　　The tool (that) he is working with is called a wrench.

　　This is the question about which we’ve had so much discussion.

　　This is the question (that) we’ve had so much discussion about.