钢管做人工接地体时，壁厚不小于（）毫米。 ["2","2.5","3.5","5"]
专职检验人员进行的检验简称（）。 ["专检","自检","互检"]
An authorized light to assist in the identification of submarines operating on the surface is a(n)（）. ["blue rotating light","intermittent flashing amber\/yellow light","flashing white light","flashing sidelight"]
Pro/E建模基础知识：以下哪组对象之间的关系是“父子关系”？（） ["“草绘平面”与“草绘参照”","“同轴孔”与其主参照：“轴A”","“阵列成员a1”与其“导引特征A”","“零件p”与“p所在的组件&rdquo"]
机械制图中规定中心线用（）表示。 ["虚线","双点画线","点画线"]
世界海上货运分布的情况如何？
