单项选择题

Questions 17 to 20 are based on the following passage. At the end of the passage, you will be given 20 seconds to answer the questions. Now listen to the passage. Learner drivers have to keep their previous jobs ______

A.because they don’ t want their present bosses to know what they’re doing
B.because they want to earn money from both jobs
C.because they cannot earn money as taxi drivers yet
D.because they look forward to further promotion