171.
W: Are you traveling alone?
M: No, I will take my family abroad this time. My wife and our three children are all going along with me.
W: What a wonderful experience that will be! I wish I could travel abroad some day.
答案解析：
正确答案为C。根据My wife and our three children are all going along with me.我妻子和我们的三个孩子都跟我一起去。可知，共有四人跟男子一起去旅行，因此B项正确。

172.
M: I thought that the chair cost 50 dollars.
W: It used to, but the price has gone up 15 dollars.
M: Well, that's more than I can afford, I'm afraid.
答案解析：
正确答案为C。椅子原价50美元，现在the price has gone up 15 dollars价格上涨了15美元，所以现在椅子的价格为65美元，因此C项正确。