Which of the following is a characteristic of a good boiler?

A characteristic of a good boiler is that it needs to accommodate expansion and contraction. As a boiler heats up, the water inside it expands, and when it cools down, it contracts. If a boiler cannot account for these changes in size, it could lead to stress on the material, causing potential damage or failure. This adaptability is crucial for maintaining the integrity and safety of the boiler system over time.

The other choices do not accurately represent essential characteristics that contribute to a good boiler. While weight and cost might sometimes factor into a boiler's quality, they are not definitive indicators of performance or safety. Materials such as plastic or glass do not provide the necessary durability and heat resistance required for boiler construction. Additionally, while many boilers do heat water, they are often capable of performing multiple functions, such as producing steam for heating and power generation, making versatility a key aspect rather than a limitation.