20. ---- What will happen if I smoke here?　　 ---- Anyone _________ here will be punished.

　　 A. seeing smoke　　 B. seeing smoking　　 C. seen smoking　　　 D. seen smoke

19. Last night I tried to call on you but your dog simply ____not let me come through the gate.

　　　 A. might　　　　 B. could　　　　 C. should　　　　 D. would

18. In my opinion , all Mr. White_____ good to his students in his class at present .He is very strict in their study.

　　　 A. does does does　 B. does do do 　C. does does do 　　　 D. did do does

17.I have some doubt _______ his words, but I have no doubt _______ he has passed the exam.

A. in; if　　　 B. of; whether　 C. about; that　　 D. to; when