单选题
Question 16-20 are based on the following dialogue:
【正确答案】
B
【答案解析】[听力原文]
M: Now would you go through that door and slip off your pullover and bra, please? I"d like to examine your breast. Do you feel any pain?
W: No.
M: Have you noticed any discharge from the nipple?
W: No, nothing like that.
M: And your periods. Are they regular?
W: No. They are a bit unpredictable. I think I must be going through the change.
M: Could you put your arms behind your head, please? Good.
W: Can you feel the lump in my breast?
M: Yes. There is no doubt a little lump in the breast.
W: What is it? Is it serious?
M: That"s what I am going to find out. I can"t tell you now what it is just by manipulating it. But the sooner we find it out, the better. So I"d like you to have some special X-rays and some blood tests.
W: What are these X-rays for?
M: Well, they can tell us where the lump is and what it may be. And I"d like you to come into hospital for your operation on Friday.
W: An operation?
M: The only way we can be sure about the lump is to take it out and examine it under a microscope.
W: Will I have to have an operation?
M: I"m afraid so, yes. The lump will have to be investigated.
W: But I don"t want to lose my breast.
M: Don"t worry. It shouldn"t be necessary. I hope it will be a minor one, and shouldn"t leave too much of a scar. But naturally it"s impossible to rule it out completely. All right? If you go along with the nurse now, she"ll take you over to the radiology department to get those pictures taken.
W: Thank you, doctor.
According to the woman, what causes the irregularity of her periods?