问题补充：
---- I must be off now. See you!
---- . See you!
A. Walk slowly
B. Nice to meet you
C. Take care
D. Be careful of safety
答案：
A. Walk slowly
B. Nice to meet you
(答案→)C. Take care
D. Be careful of safety
解析：本题考查交际用语。Take care保重。句意：——我现在必须走了，再见！——保重，再见！
