What type of water tub boiler has three drums?

• A. A type
• B. B type
• C. C type
• D. D type

Answer: (A)

The concept here is how the drum count in a water-tube boiler affects its performance. A three-drum arrangement uses three separate drums to separate steam from water and to route the water through different tube banks. That extra drum provides more surface area for heat transfer and more dedicated paths for water and steam, which helps maintain stable water levels and improve circulation in high-pressure, large-capacity service. Because the question specifies a boiler with three drums, this design fits perfectly, whereas the other listed types are built with two drums or a single drum and thus do not meet the three-drum criterion.