As the propeller turns,voids are formed on the trailing and leading edges of the propeller blades causing a loss of propulsive efficiency,pitting of the blades,and vibration.These voids are known as ______.
【单选题】The kinds of cargoes are various in international trade, from the view point of whether they need packing, they fill into three kinds:p acked cargo , bulk cargo and ______ . A.sufficiently packed carg...