听下面一段材料,回答第1至3题。 1. How many years did Professor Green teach in Renmin University? [ ] A. One year. B. Four years. C. Two years. 2. What do the two universities have in common? [ ] A. How long it takes to get a doctoral degree. B. How long a class lasts. C. How many students they have. 3. What is the woman? [ ] A. A student. B. A doctor. C. A teacher.