听第9段材料，回答第13至15题。 1. How long does the training period last? A. At least half a year. B. Two years or more. C. More than four years. 2. Why do learner drivers have to keep their present jobs? A. They don' t want their present bosses to know what they' re doing. B. They want to earn money from both jobs. C. They cannot earn money as taxi drivers yet. 3. What can we learn about the exam officers? A. They are cold and strict. B. They are experienced but rude. C. They are helpful but impatient.