A、This week. B、Several weeks ago. C、Last week. D、Last month. C由男士的回答“Since last week”可知男士的呼吸不畅问题已经出现一个星期了，故选C。

W: (16) How long have you had difficulty breathing?
M: (17) Since last week.
W: Is it very bad?
M: Yes, I feel as if I can’t get enough air.
W: Which is more difficult, breathing in or breathing out?
M: It’s harder to breathe in.
W: Are you short of breath when you’re resting or only when you’re doing something physical?
M: A little when I’m resting, but it’s worse when try to do anything physical.
W: Can you lie flat in a bed?
M: Oh, no.
W: (18) How many pillows do you use?
M: Three.
W: Do you ever wake up at night feeling short of breath?
M: Yes, I do. (19) It frightens me because I wake up feeling as if I can’t breathe.
W: What do you do when this happens? I mean, do you sit or stand up or do some movement help you breathe easier?
M: (20) If I sit up, it helps a little.
W: Let me listen to your chest. ...I can hear a few crackles and it sounds a bit wheezy.
16．What is the man’s trouble?
17．When did the man’s problem begin?
18．Why can’t the man lie flat in bed?
19．Why is the man frightened when waking up at night?
20．When his breathing problem happens，what does he do about it?