Which type of appliance is intended to supply hot water or steam for heating and processing?

The correct answer is the boiler, which is specifically designed to generate hot water or steam for heating purposes and for various processing applications. Boilers operate by heating water in a closed system, allowing it to transform into steam or hot water, which can then be distributed throughout a building for space heating, or used for industrial processes.

Heat pumps, while capable of providing heating, primarily work by transferring heat rather than generating it from a water source. They are more focused on moving heat from one place to another, rather than directly supplying hot water or steam.

Furnaces also provide heat but do so by burning fuel to create hot air, which is then circulated through ducts. Unlike boilers, they do not produce hot water or steam as a primary function.

Radiators, on the other hand, are components of heating systems that distribute the heat produced by boilers or other heating appliances. They rely on the hot water or steam supplied to them for their operation, but they do not generate heat independently.

Thus, a boiler is uniquely suited for the task described in the question, making it the correct choice.