The main purpose of warming the parts of the main engine is （）

A.to inspect if the cylinder has the water leakage
B.to expel out the residual water/gas/oil from the cylinder
C.to check if fuel supply is normal
D.A and B

A.the main engine in the stand-by condition
B.auxiliary machinery in the stand-by condition
C.dynamical equipments in the stand-by condition and could be used immediately
D.A and B

A.engine trails should be done after finishing the operation of turning the engine with the turning gear and starting the engine on air briefly
B.in the operation of engine trails, the main engine should be running in low-speed
C.As to the ship equipment with twin main engine, engine trials should be done with one engine ahead and another engine astern at the same time
D.the order “engine trials” should be given by the bridge