题干
填空。
① How much is it? ____ A. OK. Here you are.
② Can I try them on? ____ B. It's $89.
③ Is it too expensive? ____ C. It's very pretty.
④ How do you like this skirt? ____ D. Yes，it is.
答案(点此获取答案解析）
B,A,D,C
满足
，且在区间
上是增函数，则