题干
Which do you prefer to use to keep in touch with your friends, QQ WeChat?
A：and
B：but
C：or
D：SO
答案(点此获取答案解析）
C
Which do you prefer to use to keep in touch with your friends, QQ WeChat?
A：and
B：but
C：or
D：SO
中，构成从集合A到集合
的映射是（ ）
