题目

I prefer the appearance of the house; however, _____ really made me decide to buy it was the beautiful view through the window. A．which          B．what         C．that         D．where 答案：B 如图所示，质量为m的物块与转台之间能出现的最大静摩擦力为物体重力的k倍，它与转轴OO′相距R，物块随转台由静止开始转动．当转速增加到一定值时，物块即将在转台上滑动．在物块由静止到开始滑动前的这一过程中，转台对物块做的功为（                                                                                                     ）                                                                                                                                    　   A．                0    B．                2πkmgR               C．  2kmgR    D．