单项选择题
Usually, emergency electricity supplies to on board（）
A.Cargo winch B.Windlass C.Steering gear D.Main air compressor
单项选择题 Before doing any work on a hydraulic system equipped with accumulators, you should（）
单项选择题 The ability of lubricating oils to resist viscosity changes during temperature changes is indicated by the（）
单项选择题 The in the steering gear move the rudder to the required angel（）
