近年来，我国“互联网政治”渐入佳境。领导人上网了解民情、政府上网公开政务、公民上网表达意见，互联网已经成为政府和人民互动的良好平台。 网络在给人们带来便利的同时，也有一些格调不高甚至低俗的内容在网上传播。为此，国家开展了整治互联网低俗之风专项行动，严厉打击在网上传播不良信息的不法分子，净化了网络环境。 上述材料体现了政治常识的哪些知识？

A. engine trails should be done after finishing the operation of turning the engine with the turning gear and starting the engine on air briefly
B. in the operation of engine trails, the main engine should be running in low-speed
C. As to the ship equipment with twin main engine, engine trials should be done with one engine ahead and another engine astern at the same time
D. the order “engine trials” should be given by the bridge

A. 工作许可手续
B. 安全措施
C. 工作监护制度
D. 停电工作

A. 圆柱心轴
B. 圆锥心轴
C. 定位销
D. 短圆锥销