A、The British government. B、The individual post offices. C、Either the sender or the receiver of a letter. D、The local government

W: Good morning. Mr. Power’s office.
M: Good morning, I’d like to speak to Mr. Power please.
W: I’m sorry, sir. Mr. Power is busy at the moment. Would you like to leave a message?
M: Well, can I speak to Mr. Sharp then?
W: Mr. Sharp is out of town, sir. He won’t be back until next Monday.
M: I see. Well, when do you think Mr. Power will be free? I’ve got to talk to him as soon as possible. It’s very urgent.
W: He’ll be free in a couple of hours. Shall I tell him to call you back later?
M: All right. My number is 203-4657.
W: 203-4657?
M: Yes. I’ll be waiting here in the office.
W: All right, I will tell him. Good-bye.
M: Good-bye.
Q6. Why isn’t Mr. Sharp available at the moment?