听力原文：M: Good morning, Mrs. Green. You want to see me? W: Yes, Jim. Lets review what youve done so far. You were hired as a mail clerk about five years ago. Youve learned a lot since then, havent you? M: Sure. I learned more about the company because I went around to different offices. Then I was promoted to mail distribution clerk. Thats two grades higher than the mail clerk. So I skipped a grade. I went from Grade 1 to Grade 3. W: Did you like that job? M: Yeah, my pay went up, and every year I moved up a step. Every time I moved up a step, I got a pay raise. It was a Grade 3, Step F. But I didnt go outside. I was usually in the mail room. I was in charge of the other messenger clerks. W: You were a boss. M: Right. After three years, the manager said he wanted to help me move up. They gave me a little test — arithmetic, alphabetising, and some typing. W: You did well on the test. M: Yes. I did well because I studied at an adult school, and I practiced at home before the test. So I got this job as senior clerk. Im a Grade 5 now. W: Well, Jim, here is another chance to move up the ladder. The Mail Department is getting some new computers. We will give everybody two days of training. The people who learn quickly can go to school for more training. M: You mean going to school on company time? Go to school instead of coming to work? W: Yes, because it will help you in your work later. You can be promoted to production programming after youve learned to use a computer. The job starts at Grade 7. M: Well, Id like to think about it for a few days. Maybe I should stay where I am now. Questions 9 to 12 are based on the conversation you have just heard. 9. What is mainly discussed in the conversation? 10. How many years did it take the man to move up to Grade 5? 11. Who can get the chance to go to school for more training? 12. What can be inferred from the conversation?10．
A．Three years.
B．Four years.
C．Five years.
D．Six years.