17. Please don’t stand up in class until you _______.

A. were told to

B. are told to

C. were told

D. are told

18. He’s worked there since the shop opened in 1998, ______?

A. isn’t he

B. hasn’t he

C. doesn’t he

D. wasn’t he

19. The old man can hardly see anything, _______ he?

A. doesn’t he

B. does

C. can’t

D. can

20. The teacher asked the new student _______ class he was in.

A. which

B. where

C. how

D. that

21. It will be a long time _______ he _______ back from Berlin.

A. when; will come

B. before; comes

C. after; is coming

D. since; comes

22.—Are you sure that you’ve met him before?

—______ I’m mistaken.

A. If

B. Since

C. Unless

D. More than

23. Does it matter _______ it rains tomorrow?

A. that

B. whether

C. if

D. as