阅读理解。 George and Carol were medical students at the same college and like many other college students, they enjoyed playing jokes on people. Both of them smoked, but they knew that their professor was strongly against it, because smoking was dangerous to one's health. One day they decided to play a joke on their professor. At one of their medical lectures (讲座) there was always a skeleton (骨架模型) in the room so that the professor could show the students the different bones in the human body. That afternoon. Carol and George put a cigarette (香烟) in the mouth of the skeleton that was to be used for their next lecture. When the professor came in. he began talking and then noticed the cigarette. He went up to the skeleton, took the cigarette out of its mouth and said. 'You really should give them up, old boy. Look what t hey 're doing to you!' 1.What do the professor's words mean _______. A. It's only a joke to put a cigarette into a skeleton's mouth. B. He would persuade the skeleton to give up smoking. C. Smoking is really dangerous. It may even cause death. D. Students should not learn from the skeleton to smoke. 2. To whom did the professor really say these words? A. To George and Carol only. B. To the skeleton which he called 'old boy'. C. Only to himself. D. To all the students who attended his lecture. 3.The underlined word 'they' in the passage means _______. A. George and Carol B. the students C. the bones D. cigarettes 4.What do you think of the professor? A. Serious but humorous. B. Honest and foolish. C. Kind and polite. D. Hard to get along with.