参考答案：C

解析：[听力原文]M：I need a stamp for this postcard. It’s going to Arkansas. And also I’d like to send this package．W: Here is your stamp，but you have to take the package to the next window．Q：Where does this conversation most probably take place [听前猜测] 四个选项均为对话发生的地点，由此可以推断，本题问题可能是对话发生的地点。[精解] 男士说要给明信片买张邮票(need a stamp for this postcard)，还要寄包裹(send this package)。女士给了男士邮票，并且说包裹要剩下个窗口寄。可见对话发生在邮局。故正确答案为C)。