单项选择题 At normal sea going, we use （） instead of donkey boiler.

单项选择题 The soot blowers are operating in the oil fuel boiler the air/fuel ratio must （） throughout the action, and blowers greased after use.

单项选择题 Water evaporates or steam condenses at the saturation temperature, which depends upon the pressure, the higher the pressure （） the saturation temperature.