6 以下一些表达方式所在的句子一定要用虚拟语气。or(表示否则)， otherwise， unless， but for(若不是，若非)
当遇到含有以上四个表达方式的句子时，先要判断该句是表示与现在、过去、还是将来事实相反，然后依照相应的虚拟语气规则用法的形式来确定句子结构。 含有下面三个表达方式的句子体现虚拟语气的形式是固定的：
lest(以免，防备)， for fear that(惟恐)， on condition that(在。。条件下) 它们后面句子的谓语动词的形式都是：(should)+ 动词原形。
7 it is time 是。。。的时候了。这个结构有以下两种变形形式，所用虚拟语气形式都一样：it is high time / it is about time.
这三个结构后面加的句子谓语动词都用一般过去时来体现虚拟语气。 8 注意以下两种情况下should + 动词原形中should不能省略。 这里should表示一种语气，经常被翻译成“竟然”。 a. 四个动词：think， believe， expect， suspect.
它们的否定或者疑问形式后面加句子，句子谓语动词用：should + 动词原形，should不能省略。
I don’t believe that he should be cheated. 我不相信他也会被骗。 b. it is a pity， it is a shame 真遗憾，it is strange 真怪
以上三个结构后面加的句子谓语动词用：should + 动词原形，should不能省略。 错综时态的虚拟语气
错综时态的虚拟语气即指主句和从句在表达是与什么时态的事实相反上并不一致(比如主句要表达与现在事实相反而从句要表达与过去事实相反)，这种情况要采用“对号入座”的方法来处理，即主从句结构分别采用与其表达时态对应的结构。
60. If I hadn’t stood under the ladder to catch you when you fell， you _A_ now.
A wouldn’t be smiling B couldn’t have smiled C won’t smile D didn’t smile 2. If you had studied the problem carefully yesterday， _C_.
A you won’t find any difficulty now B you would not have found any difficulty now
C you would not find any difficulty now D you have not found any difficulty now
3. He would be studying at the university now if he _C_ the entrance examination.
A passed B have passed C had passed D should have passed 16. It is a shame that he _B_ that poor little girl! A deceived B should deceive C deceive D deceiving
18. Mrs. bliss kept the door and the windows shut lest the noise outside _D_ her son’s sleep. [lest(以免，防备) 后面句子的谓语动词的形式都是：(should)+ 动词原形] A would interfere with B had interfered with C interfered with D should interfere with
因篇幅问题不能全部显示，请点此查看更多更全内容