Which fuel is commonly associated with hot-water heating systems?

Hot-water heating systems can utilize a variety of fuel sources, making the answer "All of the above" correct. Each fuel type—natural gas, electricity, and oil—has its own advantages and is commonly used in different heating applications.

Natural gas is often favored in residential and commercial settings due to its efficiency, availability, and lower environmental impact compared to other fossil fuels. It provides an effective and economical option for heating water.

Electricity is another versatile option for hot-water heating systems. Electric water heaters can be simpler to install and may be more suitable in areas where gas supply is limited. They are also preferred in situations where lower operating costs or maintenance is a priority.

Oil heating systems are particularly common in regions where natural gas infrastructure is less developed. Oil burners can heat water effectively and are utilized in various residential and commercial applications, especially in colder climates.

As each of these fuel sources can independently serve hot-water heating systems, stating "All of the above" correctly encompasses the range of commonly used fuels for this purpose.