一．一般虚拟的构成：(省略if, 要将should/were/had 提到句首)
(1). 对现在的虚拟：If +S.+ did/were sth., S.+ would/could/should +do
If I had time, I would attend the meeting.
If I were you, I would seize the chance to go abroad.
(2) 对过去的虚拟：If +S.+had + p.p, S.+ would/could/should have + p.p
If you had taken my advice, you would not have failed in the exam.
(3) 对将来的虚拟：
If + S. + did/were/should do/were to do, S + would/should/could do sth.
If you came tomorrow, we would have the meeting.
If it were to rain tomorrow, the sports meeting would be put off.
If he should not come tomorrow, we should put off the meeting till next day.
注意：Had we made good preparations, we might have succeeded.
Had it not rained, we would have gone out for a walk.
Were I you, I would not do such a thing.
二． 混合虚拟：
（1） 不同时间的虚拟：If he had listened to me, he would not be in trouble now.
If he had told me yesterday, I should know what to do now.
(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：
(1).suggest, advise, recommend, propose, order, command, request, require, demand + that –clause (should do/do )
He suggested that we (should) save money for the future.(insist的判断)
(2) It is suggested/advised/ordered/requested/required that –clause(should do/do)(主语从句)
(3) My advice/suggestion/request/requirement is that-clause (should do /do) （表语从句）
His suggestion/advice/request/requirement that –clause(should do/do ) is.. （同位语从句）
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