Boilers: identify the correct statement for a water-tube boiler In water-tube designs, compare the path of water versus the path of hot gases and flames. Choose the correct option.

Concept and identification
In a water-tube boiler, the water/steam flows inside the tubes while the hot gases flow externally over the tube bank. This is the core distinction from fire-tube boilers, where hot gases are inside the tubes and water surrounds them.

Why the other options are incorrect
(b) describes a fire-tube boiler, not a water-tube boiler. (c) is too strong: many water-tube boilers use natural circulation (e.g., Babcock & Wilcox); forced circulation exists but is not universal.

Final Answer
Water passes through tubes surrounded by flames and hot gases