题目

若E、F、G、H分别是四边形ABCD四条边的中点，要使四边形EFGH为矩形，四边形ABCD应具备的条件是                                           (    ) A．一组对边平行而另一组对边不平行  B．对角线相等 C．对角线互相垂直    D．对角线互相平分  答案：C解析:略 No one tells us ________, so we need your help.A.what to do itB.what should we doC.how to do it