单项选择题 The steam boiler is part of a closed loop steam, whereby, after the energy of the steam is used up and it becomes water again, （） is collected and returned back to the boiler for heating up again to steam.

单项选择题 Care must be taken to condition the （）in the boiler to prevent scaling, and corrosion, which can weaken the pressure vessel.

单项选择题 The power and torque capability of the steering system must be such that the rudder can be swung from （）one side to（）the other side with the ship at maximum speed.