Which of the following statements concerning fire-tube boilers is correct?

Correct Answer: Option A — Combustion gases flow through the tubes.

Fire-tube boilers are defined by their design where hot combustion gases pass through tubes submerged in a water-filled shell. This configuration transfers heat from the internal gases to the surrounding water. Conversely, water-tube boilers circulate water through tubes surrounded by combustion gases, which is the opposite arrangement.