20. When you read a book, you’d better make a mark _______ you have any questions.

　 A. at which　　　　　 B. at where　　　　　 C. the place where　　　　 D. where

19. --- Look at the timetable. Hurry up! Flight 4026 ________ off at 18:20.

　 --- Ok.

　 A. took　　　　　　　 B. takes　　 　　　　　C. will be taken　　　　 D. has taken

18. John received an invitation to dinner, and with his work _______, he gladly accepted it.

　 A. finished　　　　　 B. finishing　　　　　 C. having finished　　　 D. was finished

17. Two middle-aged passengers fell into dead sea. _______, neither of them could swim.

　 A. Unfortunately　　　 B. Luckily　　　　　 C. In fact　　　　 D. Naturally

16. His movie won several awards at the film festival, ______ was beyond his wildest dream.

　 A. which　　　　　 B. that　　　　　　　 C. where　　　　 D. it