阅读短文，选择合适的答案，完成下面各题。
Mr White moved to another town (小镇). He was ill, so he went to see a doctor. He sat down in the waiting room and looked around. The doctor's diploma (证书) was hung (挂) on the wall. Suddenly Mr white remembered(记得) that there was a classmate (同班同学) with the same name in his class at the college (大学).
When he went to see the doctor, he remembered a young, nice student, but now he was sad to see an old man with grey (灰白的) hair. He said to him, "Good morning, doctor. Did you go to king's Medical college?" The doctor answered, "Yes, I did."
"Were you there from 1975 to 1979?" Mr White asked.
"Yes, I was." the doctor answered. "How did you know?"
Mr White laughed and said, "You were in my class."
"Oh," the doctor said and looked at him for a few minutes, "what were you teaching?"
