19. the football match will be put off if it ___

　　A will rain B rains C rained D is raining

　　选B

　　20. --- can I join the club,dad?

　　---you can when you ___ a bit older.

　　A get B will get C are getting D will have got

　　选A

　　此类试题较多，还包括地点，让步状语从句，并且可以用一般过去时表示过去将来，用现在完成表示将来完成

　　例如：

　　you may leave the classroom when you have finished writing.

　　非谓语动词一律在前面加not构成否定形式

　　21. I must apologize for ___ ahead of time.

　　----that’s all right.

　　A letting you not know B not letting you know C letting you know not D letting not you know

　　选B

　　22. the patient was warned ___ oily food after the operation.

　　A to eat not B eating not C not to eat D not eating

　　选C

　　含有否定意义的副词或连词放在句首时，主句部分用倒装语序

　　这种题目也比较多，现仅以not until 为例

　　23. not until I began to work ___ how much time I had wasted.

　　A didn’t I realize B did I realize C I didn’t realize D I realized

　　选B

　　24. not until all the fish died in the river ____ how serious the pollution was.

　　A did the villagers realize B the villagers realized C the villagers did realize

　　D didn’t the villagers realize

　　选A