单项选择题
A.starting and direction changing trial
B.cancelling accelerating function trial
C.lowest stable speed trial
D.continuous running trial
单项选择题 During the dock repair, each sea valve must be disassembled, cleaned and ground well.Before it reassemble the sealing surface between the valve and the valve seat should be checked by （）
单项选择题 During the dock repair, when installing the tail shaft and propeller, who should be on the spot to supervise?（）
单项选择题 When the vessel entering the dock, the first work that engineer should contact with the shipyard （）