题目

One of my classmates accidentally        he had cheated in the last examination, or he wouldn’t have got so high a mark. A．pointed out      B．let out      C．took out    D．tried out 答案：B 解析: 略已知集合A={x|y=-2x-x2}，B={y|y=2x，x＞0}，则（?RB）∩A等于（　　） A、RB、（1，2]C、[0，1]D、?