单项选择题
In ship operations，hoisting and lowering pipe in and out of the drilled hole is the main function of the（）.
A.swivel B.cathead spool C.drawworks D.stand pipe
单项选择题 In ship construction，keel scantlings should be the greatest（）.
单项选择题 In ship construction，frame spacing is（）.
单项选择题 In relation to cargo gear，what does SWL mean?（）.
