4．在表示建议、命令、要求等意义的词如suggest，order，command，require等词后的宾语从句中，谓语动词常用(should＋)动词原形，如句9。

5．由句10可以看出，在句型"It is time that..."中，从句的谓语动词可以使用一般过去时或"should＋动词原形"，should不能省略。

一、错综时间条件句

在这种条件句中，虚拟条件句即条件从句和主句所指时间不一致，因此，主句和从句的谓语动词要根据各自所指的不同时间选择适当的动词时态。

If I were you，I wouldn't have missed the film last night.

如果我是你，我就不会错过昨晚那场电影。

If they had started in the early morning，they would arrive in half an hour.

如果他们一大早就出发，再过半小时就该到了。

二、含蓄条件句

不是用条件句而是由介词或介词短语(without...，but for...)，连词(but)，副词(otherwise)或上下文等表示某种假设的情况。

Without electricity(＝If there were no electricity)，life would be quite different today.

如果没有电，现在的生活将会大不相同。

I was ill that day.Otherwise，I would have taken part in the sports meeting.

那天我病了。否则，我就参加运动会了。

三、虚拟语气在as if/though，if only后的从句中的应用

1．as if/though引导的表语从句或方式状语从句表示与事实相反的情况时也用虚拟语气。与现在事实相反用一般过去时(be动词用were)；与过去事实相反用过去完成时(had done)；与将来事实相反用"would/should/could/might＋动词原形"。

The young man with long hair walks as if he were a small girl.

留长发的那个小伙子走起路来就像个小姑娘。

2．if only表示"要是......就好了"，其后虚拟语气的用法见前面Period Three"经典句式"中讲的。

If only I had come to the party yesterday.

如果昨天我来参加晚会就好了。