A、To work in Tibet. B、To relax after work. C、To see his relatives. D、To join an international conference. B选项均以“To+原形动词”开头表明，本题考

M: I have been tired of working and need a change. So I’m just making plans to go away during Spring Festival.
W: Really? Where are you going?
M: I’m planning to visit Tibet.
W: My brother and I had a vacation there last year and we had a great time.
M: Did you get into Lhasa?
W: Sure. That’s the first stop. No one would miss Lhasa.
M: Is the Potala Palace magnificent?
W: You bet. And don’t forget the Barkhor Street. That place is full of treasures, I mean, all the exotic paintings and handicrafts, and the hand-made jewelries.
M: Well, as there is so much there waiting for me, I guess I should stay longer.
W: Definitely.
M: I heard that the weather there is great.
W: Well, that depends on how you define "great". No humidity, but it could be extremely cold in winter. Besides, you do need to be careful about high altitude.
M: What should I do about that?
W: Oh, just take it easy for a few days. Don’t exercise too vigorously. Just do everything gradually.
M: I’m sure I will be fine. And I will let you know all about my trip when I come back.
Questions 9 to 12 are based on the conversation you have just heard.
9. What’s the main purpose of the man’s trip?
10. Why does the woman know so much about Tibet?
11. What can be inferred about the weather in Tibet during Spring Festival?
12. According to the woman, what may cause the man the most problems in Tibet?