单项选择题When the engine room is put in standby condition, the engineer in charge of the watch need not to()
A.ensure all machinery which may be used during maneuvering is in ready
B.ensure an adequate reserve of power is available for steering gear and other requirements
C.keep the main propulsion unit controls continuously attended when in the manual mode of operation
D.ensure all machinery which may be used during maneuvering is running stably