时态特殊用法.ppt

一、 在条件状语从句、时间状语从句、让步状语从句中，如果主句是将来时或主句是祈使句，从句中要用一般现在时代替一般将来时。如： I’ll not go unless I’m invited. Tell him the news as soon as he comes. 二、 “used to/ would + 动词原形” 可以表示过去经常或习惯性的动作。如： Often at night she would hear a long low whistle and the sound of a metallic noise. 三、 “be + to do” 表示拟定或计划中将发生的行为或按职责义务必须去做的事情；“be about to do”表示即将发生的事情，句中一般不使用时间状语。如： No one is to leave the room without permission. 四、 某些固定句式中的动词时态 1）This / It is the first/second… time + that 从句。that从句一般用现在完成时，如果把前边的is 改为was, 则that从句用过去完成时。如： This is the first time I have come here. It was the third time that he had made the same mistake. 2) It is / has been + 一段时间+ since从句。Since从句中一般用一般过去式，如果将前边的is 改为was, 则since从句中用过去完成时。如： It was ten years since we had such a wonderful time. 3) be about to do… when…意为“即将… … (这时)突然… …”。如： I was about to go out when the telephone rang. 4) be (was/were) + doing … when…意为“正在干… …(这时)突然… …”。如： They were reading when Tom shouted in pain. 5) be on the point of doing sth. When… … “正要做某事时突然… …”如： He was on the point of going out of his office when the telephone rang. 6) 在包含Hardly had … done… when…；No soon had … done … than…的句型中主句用过去完成时，从句用一般过去时。意为“刚… … 就 … …”。如： Hardly (No soon) 7) It + be +一段时间 + before 从句 It was some time before … 一段时间之后才 … … It was not some time before … 没过多久就 … … It will be some time before … 一段时间后才会 … … It won’t be some time before… 过不了多久就会 … … 如果主句用将来时，则从句用一般现在时表将来，意为多长时间以后即将发生某事；如果主句用过去时，从句也用过去时，意为多长时间后发生了某事。如： It won’t be long before he succeeds. It was ten years before they met again. 五、一般现在时 1. 在表示时间、条件的状语从句中，用一般现在时表示将来的概念。如： If it rains tomorrow, our picnic will be put off. 如果明天下雨的话，我们的野餐就得推迟了。 I’ll have a hot bath as soon as I get home. 到家后我就洗个热水澡。 2. 在make sure / be certain / hope / suppose / assume等后的宾语从句中，可用现在时表示将来，也可用将来时表示将来。如： I hope my sister comes (will come) tomorrow. 我希望姐姐明天来。 3.瞬间动词的一般现在时可以表示将来，表示按计划安排好了将要发生的动作。此类动词包括 come, go, leave, arrive, start, take off, close, open, end, stop, depart, return等表示开始或移动意义的词。如： The train leaves at eight o’c