【单选题】
Directions:
For each blank in the following passage, there are four choices given below and markedA,B,
C、andD、Choose the one that is most suitable and mark your answer by blackening the corresponding letter on theAnswer 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.