题目

I don't skate now, but I___________ when I was a kid.    A. used to     B. am used to it  C. sued     D. used to do   答案：A本题是词语辨析。used to表示“过去常常”，后面常接动词原形，be used to 后接动词-ing形式，名词或代词，表示“习惯于……”。如果yx=2，那么y2-xy+x2y2+x2的值为（　　）A．45B．1C．35D．2