单项选择题
Permission is kindly requested（）the ballast water.
A.pump out B.to pump out C.pumping out D.be pumped out
单项选择题 On a ship，a door that is required to be marked KEEP CLOSED is designed to（）.
单项选择题 Limit switches are used on which davits?（）
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?（）.
