North Korea threatens to from six-party talks unless its proper rights are to be satisfied. A.escape B.flee C.withdraw D.retire 答案:C6.a、b是截面为直角三角形的两个完全相同的楔形物体,分别在垂直于斜边的恒力F1、F2作用下静止在相同的竖直墙面上,如图所示.下列说法正确的是( )A.a、b受力个数一定相同B.F1、F2大小一定相等C.墙面对物体的弹力一定相等D.b受到摩擦力可能大于a受到的摩擦力