听一段材料，回答下面几个小题。
How far did they walk every day during the trip?
A. 10 kilometers.
B. 15 kilometers.
C. 20 kilometers.
What problem did they have?
A. They didn't have modern equipment.
B. There wasn't enough oxygen sometimes.
C. They couldn't walk freely in the mountains.
What did the woman enjoy most about the trip?
A. Clean air.
B. Delicious food.
C. Beautiful sunshine.