In a fire tube boiler, the heat and gases of combustion pass through which of the following?

In a fire tube boiler, the correct choice is that the heat and gases of combustion pass through the tubes. Fire tube boilers are designed with tubes that carry the hot combustion gases produced by burning fuel. These tubes are situated within the body of water contained in the boiler. As the hot gases move through the tubes, they transfer heat to the surrounding water, which in turn generates steam.

This design allows for efficient heat transfer, as the large surface area of the tubes in contact with the water facilitates effective heating. The gases of combustion are contained within the tubes, which is why the term "fire tube" is used to describe this type of boiler. The boiler shell itself surrounds the water and the tubes but does not come into direct contact with the combustion gases. Similarly, the firebox is where the actual burning takes place but does not carry the gases through the system; instead, it is the tubes that play this critical role in transporting the heat from combustion to the water to create steam.