Which is false about engine trials?（）

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