知觉
滚齿机（），会使刀架滑板升降时产生爬行。 ["垂直导轨变形","润滑油管阻塞","丝杠轴向窜动","螺母磨损","交换齿轮间隙过大"]
尿素合成塔设置塔板的作用（）。 ["防止返混，提高尿素转化率","为了设备安全运行","增加产量","增加塔器机械强度"]
美国学者迈克尔波特将国家优势的发展阶段分为四个阶段，即要素驱动阶段、投资驱动阶段、（）、财富驱动阶段。 ["科技驱动阶段","人才驱动阶段","创新驱动阶段","理论驱动阶段"]
You want to limit access to a method of a public class to members of the same class. Which access modifier accomplishes this objective？（） [" Public"," Private"," Protected"," Transient"," No access modifier is required"]
自认
