21. _______ their service, the workers of the hotel are active in learning English.
A. Improving B. To improve
C. Improve D. Having improved
22. – She is a little selfish. _______, she only cares about herself.
-- No wonder she is so unpopular.
A. What’s more B. In other words
C. By the way D. On the contrary
23. All possible means _______to rescue the miners trapped underground so far.
A. have been tried B. has been tried C. is being tried D. is to be tried
24. An American scientist and writer _______ coming to give us a lecture on English
learning methods when he visits our school.
A. was B. were C. is D. are
