For each blank in the following passage, there are four choices given below and marked A, B, C and D. Choose the one that is most suitable and mark your answer by blackening the corresponding letter on the Answer Sheet.

　　Smoking, which may be a pleasure for some people, is a serious source of discomfort for their fellows. _21_, medical authorities express their concern about the effect of smoking _22_ the health not only of those who smoke but also of those who do not. In fact, non-smokers who must involuntarily inhale (吸入) the air _23_ by tobacco smoke may suffer more than the smokers _24_.

　　Smoking is prohibited in the theatres and in halls used for showing films _25_ in laboratories _26_ there may be a fire hazard (危险). Elsewhere, it is up to your good _27_.

　　I am _28_ asking you to maintain “No-Smoking” in classrooms and seminar rooms.

　　This will prove that you have the _29_ health in mind, which is very important to a large _30_ of our students.

　　21.A. Still B. Further C. More D. Again

　　22.A. in B. to C. on D. with

　　23.A. polluting B. be polluted C. polluted D. to be polluted

　　24.A. them B. themselves C. their own D. they

　　25.A. and B. but C. as well as D. also

　　26.A. where B. which C. that D. how

　　27.A. feeling B. sense C. realize D. think

　　28.A. so B. next C. therefore D. and

　　29.A. non-smokers B. non-smokers’ C. non-smoker’s D. non-smoker

　　30.A. number B. amount C. many D. much

　　参考答案：21.B 22.C 23.C 24.B 25.C 26.A 27.B 28.C 29.B 30.A