Question 150Steam Plants - Assistant Engineer

The correct answer is D) soot blower elements. The soot blower elements are responsible for cleaning the boiler tubes by directing high-pressure steam or air onto the tubes, dislodging any accumulated soot or debris. This is a critical function in maintaining the efficiency and proper operation of the boiler. The other options, such as main generating tubes, superheater tubes, and screen tubes, are different components of the boiler that have specific functions, but they are not indicated by the arrow "O" in the provided illustration.