根据下列句子的提示，写出空缺处各单词的正确形式。

51．There must be some m __________--- I already paid my pill.

15. -- Is Mrs. Gao teaching in Wenzhou?

　 ---She ________. But now she is teaching in Hangzhou.

A. is　　　　　　　　　　　　　　　 B. has　　　　　　　　　　　 C. was　　　　　　　　　　 D. had

14. -Janet, I’ll go for the table tennis match this afternoon . - _______. I hope you win the game.

A. Very well.　　　 　B. See you.　　　 　C. Good luck! 　　　D. Congratulations!

13. --- The light in the office is on. Who is there?

--- It _______ be Mr. Lin. He always works hard.

--- No, it _______ be him. He is on holiday.

A. may; can　　　　 B. must; mustn’t　　　 　C. must; can’t　　　 D. may; mustn’t