Go back to your seat, please.
Take a ten-minute break now.
Don't walk on the grass.
Don't write in your book.
Let's rest for a while now.
Let's not watch TV tonight.高二unit 15 A Famous Detectative由www.yf1234.com收集及整理,转载请说明出处www.yf1234.com
www.yf1234.com 虚拟式是说话人为表示一种假设的情况、一种主观的愿望，即认为动词所表示的动作或状态并非事实或仅是主观设想时所用的动词形式。虚拟式在现代英语中不是以个重要的语法范畴。现代英语表达虚拟式的口气可采用多种多样的语法手段，如采用一般过去时、过去进行体，过去完成体：
It's time we had a rest.
I was wondering if you would let me use your car.
How I wish I had gone there with you!
还可采用情态助动词的过去时形式加动词不定式或不定式完成体：
I should/would be there by now if I had started earlier.
He would have been there by now if he had not missed the train.
当然也可采用一种特殊的动词形式，即虚拟式。
现代用于的虚拟式并不像传统语法描写的那样复杂，它只有两种形式，即be-型虚拟式(BE-SUBJUNCTIVE)和were-型虚拟式()WERE-SUBJUNCTIVE)。
be-型虚拟式
用于表示命令、决定、建议等词语之后的that-分句中; 用于由if,though,etc引导的分句中; 用于某些公式化语句中
were-型虚拟式
用于某些状语分句中; 用于某些名词性分句中
虚拟式/be-型虚拟式
be-型虚拟式是以动词原形表示的，既不管主语是什么人称，动词一律用原形，如I go, you go, he go后者I be, you be, he be。如果动词为被动态，则助动词be也一律用原形，如I be sent, you be sent, he be sent。因此，如果主语是复数，便显示不出虚拟式与陈述式的区别；除了虚拟式be与陈述式am/is/ are/was/were有所区别外，其他动词的be-型虚拟式只有在单数第三人称主语之后才是由标记的。
be-型虚拟式的主要用法如下。
用于表示命令、决定、建议等词语之后的that-分句中
be-型虚拟式的这一用法又有以下三种情况：
a)用在decide, decree, demand, insist,moveorder,prefer,propose,recommend,request,require,suggest,vote等动词之后的that分句中。例如：
He ordered that all the books be sent at once.
We propose that somebody neutral take the chair(担任主席)。
She insisted that she go to the south for her holiday.
Congress has decided /voted/ decreed that the present law be maintained.
The doctor insisted that he not eat meat.
b)用在decision, decree, demand, Instruction, order, requirement, resolution等名词之后的that-分句中。例如：
The board(理事会) has given instructions that the agent fly to Boston.
We were faced with the demand that this tax be abolished.
Your advice that she wait till next week is reasonable.
Their decision was that the school remain closed.
His order that the troops not be sent at once was carried out.
在这一用法中be-型虚拟式能与“should +不定式”交替使用，也能与不定式被动语态交替使用。例如：
He ordered that the books be sent at once.
=He ordered that books should be sent at once.
=He ordered the books to be sent at once.
It is important that she be placed in an appropriate job.
=It is important that she should be placed in an appropriate job.
=It is important for her to be placed in an appropriate job.
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高二unit 15 A Famous Detectative