单项选择题在挺柱工作时，由于受凸轮侧向推力的作用会引起挺柱的侧面和底面磨损不均匀。因此在结构上采取了使挺柱旋转的措施。（）A.对B.错
单项选择题1.Compared with Pictures of the Ode to the Goddess of the Luo River, The Riverside Scene at Qingming Festival is a more realistic, and vivid depiction of the ship's pattern in the Song Dynasty.( )
