Which areas are most commonly prone to leaks in boiler systems?

The correct answer is focused on the components that are commonly involved in leak formation within boiler systems. Boiler tubes, fittings, valves, and flanged joints are critical parts of the boiler infrastructure where leaks are most likely to occur.

Boiler tubes can be subject to extreme temperatures and pressures, making them vulnerable to wear and potential failure over time. Fittings, which connect various sections of piping, may develop leaks due to vibrations or thermal expansion and contraction. Valves, used to control the flow of fluids, are also susceptible to leaks, particularly where seals may degrade. Flanged joints, which join two sections of piping, can experience leaks if bolts are not adequately tightened or if the gasket material degrades.

This answer encompasses all the critical areas in a boiler system that can develop leaks due to their operational demands, highlighting why this option is the most comprehensive representation of where leaks commonly occur. The other choices are too limited in scope or focus on a single component, overlooking the multiplicity of areas where leaks can arise.