19. Guest: Oh, I hadn’t realized how late it was. I’m afraid I’ll have to be going.
Host： Oh, not yet. I’m just going to make some coffee.

Guest: ___, though I’d really love to stay. I’ve got to be up by six tomorrow morning, unfortunately. Thank you for a wonderful party.

(3分)
A. I’m sorry, but I must
B. Pardon me, but I should go
C. It’s a pity, but no way out
D. Excuse me, but I have to go

---