【单选题】

Speaker A: I'm terribly sorry, but something unexpected has come up and I won't be able to keep my appointment with you this afternoon. I wonder if we could change the time of Our meeting to sometime tomorrow morning.Speaker B: ______
A．Thanks for calling. I'll expect you at the same time tomorrow morning.

B．OK. Let's meet each other later today.
C．Don't worry. First things first.
D．I'm sorry. I won't be free the whole morning. What about tomorrow afternoon