anywhere in public, by simply _________their smart phones.

A. which; use B. which; using

C. of which; use D. of which; using

21. _________ more and more forests damaged, some animals and plants are facing the danger of dying out.

A. As B. For

C. With D. By

22. _________, the student insisted that he should be separated from his roommates, who were noisy.

A. To avoid being affected B. To avoid to be affected

C. Avoiding being affected D. Avoiding to be affected

23. I'd appreciate _________ if you would like to teach me how to use the expression once more and I always appreciate _________ me with my English in the past.

A. that; you to help B. this; your helping

C. it; you to help D. it; your helping

24. The government has taken some measures to solve the shortage of electricity, but it will be some time_________ the situation improves.

A. since B. when

C. unless D. before

25. I had been out of touch with Allen for many years but the moment he called me up that day, I ________ his voice.

A. understand B. recognised

C. remembered D. knew

26. Internet shopping will be ready to _________ when people may think that it is safe.

A. take over B. take on

C. take off D. take in

27. An advantage of living on the top floor of a high rise building is that you can get a good