单项选择题
In the piping systems of a vessel，what type of valve gives the least resistance to fluid flow when fully open?（）.
A.Globe valve B.Butterfly valve C.Gate valve D.Packless valve
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（）.
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（）.
