题目

— We could have walked to the station. It was so near.— Yes. A taxi ____ at all necessary. A . wasn't B . had been C . wouldn't be D . won't be 答案：A如图所示，一个质量为1kg与竖直墙壁接触的物体在水平推力F=20N作用下保持静止，物体与墙壁间的动摩擦因数为0.6，则墙壁对物体的支持力为_______N，物体所受的摩擦力为______N．物体重力的反作用力的受力物体是___________．