21. Ray: Hello, Susan. It’s Ray. Is this a good time to talk?
Susan: Um, not really. _______________
Ray: OK, can I call you back later?
Susan: Sure! Call me in an hour! I really have to go now!
(A) I am so sorry to hear that.
(B) I will have fun.
(C) I am late for a meeting.
(D) I cannot agree more.