After a boiler has been taken off the line and is cooling, the air cock is opened to __________.

Correct Answer: Option B — prevent the formation of a vacuum within the boiler

In USCG Steam Plants (Boilers & Turbines), regarding 'After a boiler has been taken off the line and is cooling, the air cock is opened to', the verified engineering fact is: 'prevent the formation of a vacuum within the boiler'.