单项选择题
What is/are the advantage（s）of cranes over conventional cargo booms（）.
A.Cranes are able to pick up and drop loads over a greater spotting area B.Increased safety because the deck is clear of running and standing rigging C.Simplicity of operation of the crane by its operator D.All of the above
单项选择题 What is the purpose of the equalizing beam aboard a crane vessel（）.
单项选择题 What is meant by the term“luffing the boom”of a crane（）．
单项选择题 What does “evel-luffing” accomplish during crane operations（）.
