A、  B、  C、  C所给出的问题是询问对方是否搭乘过出租车从办公地点到机场。选项(C)的回答Yes搭乘过，并且补充说出租车费花了50美元，很贵。是符合语境的正确答案。

What’s in the big envelope?
(A)I’m not sure who left it there.
(B)There’s a larger one if you need it.
(C)The extra office keys.

Have you ever taken a taxi from the office to the airport?
(A)No, I think their office is on the thirtieth floor.
(B)No, I usually book my tickets online.
(C)Yes, and it was expensive —about fifty dollars.