Directions:

　　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. _51_, medical authorities express their concern about the effect of smoking _52_ 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 _53_ by tobacco smoke may suffer more than the smokers _54_.

　　Smoking is prohibited in the theatres and in halls used for showing films _55_ in laboratories _56_ there may be a fire hazard (危险). Elsewhere, it is up to your good _57_.

　　I am _58_ asking you to maintain “No-Smoking” in classrooms and seminar rooms.

　　This will prove that you have the _59_ health in mind, which is very important to a large _60_ of our students.