单项选择题
A.the sinking of tail shaft
B.the clearance of stern bearing
C.the total flexure of shaft
D.main engine crankshaft deflection
单项选择题 （），where the ship is docked for hull coating renewal, and for any other required underwater work to be carried out, when the opportunity is taken to make other repairs.
单项选择题 A is the documentary attestation for the delivery of stores and spare parts（）
单项选择题 The purpose of treating the cooling water of the diesel engine is to（） Ⅰ. resist the scale formation in the cooling chamber Ⅱ.lubricate the engine part Ⅲ.increase thermal capacity Ⅳ.resist corrosion