6.It is natural/necessary/strange +that从句 (should) do表惊奇、怀疑、惋惜、不满、理应如此等。

　 　It’s strange that he should have missed the train. (表竟然)

　 　It is important that we should learn from others.(表理应如此)

　 　It is a pity that he should not go with us.(表惊讶、不满)

5.His suggestion/advice/request/requirement…+ 同位语从句(should )do+ is..

　　The request that they should get more is reasonable.

4.My advice/suggestion/request/requirement/order/proposal…+ is +表语从句(should)do

My advice is that you should practise speaking English as often as possible.

The order from the commander was that the troops should set off for the front immediately.

3.It is suggested/advised/ordered/requested/required…+ that从句(should) do

It is proposed that more students should go to university.

2.suggest, order, propose, request, require, demand, advise, insist+ 宾语从句(should )do

He suggested that we (should) save money for the future.

The undergraduate insisted that he (should) go to work in the south.

注意：当suggest表示暗示，insist表示坚持观点,事实时，后接的宾语从句应当用真实语气。

His silence suggested that he agreed with my decision.

He insists that doing morning exercises does good to people’s health.

1.省略连词if。在书面语中，如果虚拟条件从句中有were，had 或 should，可以把if省略，把这几个词放到主语之前，构成主谓倒装。

　Should he come (If he should come), tell him to ring me up. 他要是来了，让他给我打个电话。

Were I you (If I were you), I would not do it. 我要是你，就不做这事。

2.虚拟与陈述的混合

He could have passed the exam, but he wasn’t careful enough.

You should have come earlier. The bus left a moment ago.

(三)特殊句式虚拟结构

1.不同时间的虚拟

If he had listened to me, he would not be in trouble now.(从句与过去事实相反，主句与现在事实相反)

If he had told me yesterday, I should know what to do now. (从句与过去事实相反，主句与现在事实相反)

If I were you, I would have gone to her birthday party. (从句与现在事实相反，主句与过去事实相反)

If you hadn’t lent me some money, I couldn’t have bought the new house and most likely I would be still living in the dangerous house now. (从句与过去事实相反，and后面的主句与现在事实相反)

(一)一般虚拟结构　　

注意:主句中的should只用于I、we，但在美国英语中，should常被would代替；从句中的should可用于各种人称，且不可以被would所代替。

(二)混合虚拟结构

11.其它情态动词

　 　①have to

have to表示 “必须, 不得不”, 在这个意义上与must很接近, 但must表示的是说话人的主观看法, 而

have to表示的却是客观需要. have to比must有更多的形式。

The TV set is broken. I have to buy a new one.

The students will have to know how to use the computers.

注意：在回答must的问句时, 否定式常用need not(needn’t)或don’t have to表示 “不必”。而不用

must not, 因为must not表示 “不可以”。

　 ②used to

表示过去的习惯动作或状态(现在已不复如此)

-Did you use to go there to see your brother? /Used you to go there to see your brother?

-Yes, I did(used to). /No , I didn’t (usedn’t).

注意：would也可表示过去反复发生的动作或某种倾向，但是不涉及到现在。

③had better

表示 “最好(做……)”

We had better go now.　

　　 其否定式为had better not