Answer:
Correct answer is option D
Step-by-step explanation:
Electric baseboard is not a correct option because it is very expensive.
Forced-air is and hot water are also not correct option because they are less efficient and more expensive in comparison to steam.
Steam as a central heating system is often used when heating many buildings from a central location because it is less expensive and more efficient. For generating steam, solar energy or fossil fuels are used. Steams is passed in the whole buildings through pipelines from a central location.