听力原文：M: Excuse me. I believe you're the one I'm looking for. My name is Arnold Bixby. I came to apply for a job. W: Oh, sure. The boss told me you were coming. My name's Mary. I'm the foreman here, and I do the hiring. I thought you weren't going to show up. M: I tried to call you, but I couldn't get through. I wanted to cancel our appointment. W: What happened? You find a job already? M: No, I'm still looking, but construction work is just something I'm not qualified for. W: This here's the office. Go on in and set yourself down. What do they call you anyway? Arnie? M: People call me Arnold. W: OK, Arnold. Now what's this all about? The boss told me you wanted a job real bad. M: Well, it's true I need a part-time job. W: You mean you can't work full-time? M: No, I have to go to school too. W: School! Boy, they couldn't get me to go back to school if they paid me. M: Believe me, they're not paying anybody. W: What do you study over there at the university? M: I'm in chemistry. W: Afraid we haven't got any jobs for chemists here? But we could put you on as a cement-mixer. How's that? M: You must be putting me on. Look, this is some kind of mistake. Questions 19 to 21 are based on the conversation you have just heard. 19. Who is the woman? 20. Why did the man want to cancel the appointment? 21. What major is the man in? (20)