题目

The island country had fought _________ the invaders for more than ten years _________it became an independent republic. A . against; before B . against; when C . with; since D . for; while 答案：A如图所示，质量为M的物体放在光滑水平地面上，受与水平方向成α角的恒定拉力F作用’从静止开始沿水平地面运动，在时间t内，拉力F’对物体所做的功为W．若仅改变上述某一个量，物体还是从静止开始沿水平地面运动，下列可使拉力做的功为2Wr的是（ ）A．物体质量减小为B．拉力增大为2F；C．做功时间增长为2tD．α角从60°变为0°