题目

 The newspaper says if more underground lines          next year, it will be much easier for people to travel around Nanjing.       A. will be finished          B. have finished             C. are finishing              D. are finished 答案：D如图所示，重为G的物体静止在倾角为α的粗糙斜面体上，现使斜面体向右做匀速直线运动，通过的位移为x，物体相对斜面体一直保持静止，则在这个过程中（ ）A.弹力对物体做功为GxcosαB.静摩擦力对物体做功为GxsinαC.重力对物体做功为GxD.合力对物体做功为0