听力原文：W: Hello. Is this the registration office? M: Yes. This is Herbert speaking. How can I help you? W: Well, I have a slight problem here. I have been in Chemistry 302B class for a month, and today Prof. Smith told me I wasn't registered in his latest class list. I thought all the while I was registered in his class and this really comes as a surprise. M: Well, why don't you give me your student ID and I'll just check to see if you are officially registered. W: 39241. M: Just a minute. And you are Alice Jones, right? W: Yes, that's me. M: Alice, the computer shows that you are registered in Chemistry 302A and that's Dr. Nelson's class. Perhaps you have mixed up the two. W: Oh no, I thought I'd made a switch from Nelson to Smith. How did this confusion occur? I dropped Nelson's class and switched to Smith's in the first week. I still have the add/drop form. with me. M: In that case, I suggest you come to the registration office with the add/drop form. and we'll try to sort it out for you. I don't rule out there could have been a mistake that occurred during the add/drop process. W: I'll be there first thing in the morning to sort out this mess. You know, I wouldn't want to switch professors when I'm now half way through. M: I can understand that．See you tomorrow． (20) A．She found she wasn't registered in Chemistry 302