A、Damage to the equipment. B、The man’s wrong operation. C、The line upgrading. D、It was unclear. C女士回答说：可能由于电信公司的电路升级而造成了一些用户的电话信

W: Good afternoon. This is Jane speaking. How can I help you?
M: Hi, I am calling in regards to a cell phone I bought from you a while back. I am afraid there is something wrong with the reception signal on my hand phone. I can’t seem to get incoming and outgoing calls and it always gives me a busy signal.
W: Could you tell me how long this has been happening? I ask that because it will likely tell me whether the problem is with your equipment or reception.
M: A couple of days ago. Initially I thought it could be the hand phone’s problem but then I realized it was probably the receiver signal.
W: Please give me your number and I will check whether there is any problem on the line.
M: 9988777.
W: Thank you. Please hold onto the line and I will get back to you in a minute.
M: Sure.
W: Sorry to keep you waiting, Sir. I have checked your number and everything is fine. It could be due to our line upgrading and sometimes it could affect certain mobile numbers. Our apologies for your inconvenience.
M: How long do I have to wait before the signal returns to normal?
W: Well, another couple more days. I will give this feedback to our technician and if the problem still exists after two days, please give us a call and we will help you to solve it.
M: Oh—but you bet I will phone if I don’t get this fixed soon. It’s not as if I can do without my cell phone for very long.
1. What is the problem with the man’s cell phone?
2. Why does the woman ask the man how long the problem exists?
3. According to the woman, what could have caused the problem?
4. What does the man imply at the end of the conversation?