If the towline parts，you should（）. start towing by pushing ahead。 abandon the towing vessel。 retrieve the tow bridle。 relieve strain on the retrieving line。
“合并拷贝”操作，对于下列（）有效。 隐藏图层。 处于某图层组中的图层。 被锁定的图层。 背景图层。
Cast iron and gunmetal fittings are used freely in small sizes at moderate pressure; large fittings, those for high pressure and temperature are cast or mild steelIn the above sentence, the word “those” means （）. east iron firings。 mild steel fittings。 small fittings。 large fitting。
If the towing bridle legs are not of equal length（）. excessive strain is placed on the shorter leg。 the shorter leg may fail。 the longer leg is slack。 All of the above。
在扒装珠光砂时要注意哪些安全事项？
游梁式抽油机调冲次操作中，准备工具不包括（）
