23. I can hardly imagine Peter _______across the Atlantic Ocean in five days.

A. sail　　　　　 B. to sail　　 C. sailing　　　 D. to have sailed

22. Was it at the crossing ________the accident happened?

A. at which　　 B. where　　 C. that　 D. there

21. -------What would you like to say about your last trip through the desert?

------Nothing _______more important than water.

A. must have been　　　　　　 B. could have been

C. might be　　　　　　　　　 D. is

20. ------where ______ Margaret have put the empty bottles?

-------- She ________ them away. They must be somewhere.

A. Can; can’ t have thrown　　 B. must; needn’ t

C. must; must have thrown　　 D. can; must throw

19. The great success, ________by different-field scientists hard working for years greatly encourages the whole country.

A. achieving　 B. achieved　 C. was achieved　 D. to achieve

18. With its goal _______the first class of the world, the university is now trying its best.

A. aimed at　　 B. aiming at　 C. to aim at　　 D. aim at

17. As soon as the suggestion was ______, people showed great interest in it.

A. put out　　 B. put up　　 C. put forward　 D. put on

16. ------ can you work out this difficult exercise?

-------- Though difficult, I still think it ______my ability.

A. without　　 B. within　 C. beyond　 D. inside

15. ------it looks as if a storm is coming up.

-------- Yes, _______.

A. it certainly does　 B. it certainly is

C. it looks so　　　　 D. it is coming

14. Only by doing the work themselves, ________.

A. the students will get experience

B. the students will be sure to get experience

C. will the students get experience

D. will be the students sure to get experience