补全对话。选择方框内的句子完成对话（其中有两项是多余的）。
A: Excuse me. Would you mind helping me?
B:             What’s up?
A: One of my American friends invited me to her house on Christmas Day ,but I don’t know much        about the customs and manners.       
B: Sure.When are you supposed to get there?
A:     
B:Well, the first thing is that you should get there on time.
A:All right.       
B: You are supposed to say “Merry Christmas” .
A: OK.