单项选择题

案例分析题

M Hello，I got this paper on my door.I guess I wasn’t home to receive a package.
W O.K.We can get it for you，but you’ll have to take a number and wait for your turn.There are numbers on the wall behind you.
M Oh，I didn’t see them.Where can I get an envelope to send this letter？
W They are by the front entrance.You can just put it in the envelope and pay for it when it’s your turn.

Where might this conversation be heard？（）