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一般现在时的被动,has to do不得不做某事,be done被动语态;
英语时态分为16种:一般现在、一般过去、一般将来、过去将来时,以及这四者的进行时、完成时和完成进行时。列出具体几种:
一般现在时:用法:A) 表示现在发生的动作、情况、状态和特征。B) 习惯用语。C) 经常性、习惯性动作。例:He always helps others. 他总是帮助别人。D) 客观事实和普遍真理。尤其要注意,如果前后文不是一般现在时,则无法保持 主句、从句时态一致。
E) 表示一个按规定、计划或安排要发生的动作,(仅限于某些表示“来、去、动 、停、开始、结束、继续”等的动词)可以与表示未来时间的状语搭配使用 。常见的用法是:飞机、火车、轮船、汽车等定期定点运行的交通方式。例:The next train leaves at 3 o'clock this afternoon.下一趟火车今天下午3点开车。How often does this shuttle bus run? 这班车多久一趟?
F) 在时间和条件状语从句里经常用一般现在,有时也用现在完成时表示将来事情,例:When you have finished the report, I will have waited for about 3 hours.等你完成这份报告的时候,我就已经等了将近3个小时了。
现在进行时(be doing)用法:现在正在进行的动作。
现在完成时(have done)用法:A) 表示动作到现在为止已经完成或刚刚完成。例:I bought a new house, but I haven't sold my old one yet, so at the moment I have two houses.
B) 表示从过去某时刻开始,持续到现在的动作或情况,并且有可能会继续延续下去。此时经常用延续性动词。时间状语常用since加一个过去的时间点,或for加一段时间,或by加一个现在时间。例:Great as Newton was, many of his ideas may be challenged today and are being modified by the work of scientists of our time.虽然牛顿是个伟大的人物,但他的许多见解直到今天还在受到挑战,并且被现代科学家的工作所修正。
现在完成时,但一般都这么说:have/has done,have/has been done,是现在完成时的被动语态。现在完成时表示到说话时为止(或到现在为止)已经发生或完成了(不一定结束)的动作或状态。
Have 表示动作,如表示“吃(=eat)”“喝(=drink)”“拿(=take)”“收到(=receive)”“度过(=spend)”等时,在用法应注意以下几点:
(1) 可用于进行时态,但一般不用于被动语态。如:
误:Lunch is had by him.
正:He is having lunch. 他在吃中饭。
(2) 不与 got 连用。如:
误:I’d like to have got a look at it.
正:I’d like to have a look at it. 我想看看它。
(3) 一般不用缩略式。如:
误:We’d a good time at the party.
正:We had a good time at the party. 我们在晚会上玩得很高兴。