含有下面三個表達方式的句子體現虛擬語氣的形式是固定的：

　　lest(以免，防備), for fear that(惟恐), on condition that(在..條件下)

　　它們后面句子的謂語動詞的形式都是：(should)+ 動詞原形。

　　7 it is time 是...的時候了。

　　這個結構有以下兩種變形形式，所用虛擬語氣形式都一樣：it is high time / it is about time.

　　這三個結構后面加的句子謂語動詞都用一般過去時來體現虛擬語氣。

　　8 注意以下兩種情況下should + 動詞原形中should不能省略。

　　這里should表示一種語氣，經常被翻譯成“竟然”。

　　a. 四個動詞：think, believe, expect, suspect.

　　它們的否定或者疑問形式后面加句子，句子謂語動詞用：should + 動詞原形，should不能省略。

　　I don't believe that he should be cheated. 我不相信他也會被騙。

　　b. it is a pity, it is a shame 真遺憾，it is strange 真怪

　　以上三個結構后面加的句子謂語動詞用：should + 動詞原形，should不能省略。

　　錯綜時態的虛擬語氣

　　錯綜時態的虛擬語氣即指主句和從句在表達是與什么時態的事實相反上并不一致(比如主句要表達與現在事實相反而從句要表達與過去事實相反)，這種情況要采用“對號入座”的方法來處理，即主從句結構分別采用與其表達時態對應的結構。

　　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，防備) 后面句子的謂語動詞的形式都是：(should)+ 動詞原形]

　　A would interfere with B had interfered with

　　C interfered with D should interfere with