A：gain
B：request
C：rescue
D：require
下面句中有一处错误，请找出来并改正。
What does the child have on breakfast?
____
We will hear what he must say and observe what he will do for what he says and what he does often _______.
下列事例中，能减小摩擦力的是（ ）
已知F1,F2是双曲线的两个焦点，Q是双曲线上任一点（不是顶点），从某一焦点引∠F1QF2的平分线的垂线，垂足为P，则点P的轨迹是( )
