Machines can be fueled by various sources of energy, depending on their design and purpose. Here are some common fuel sources:
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Energy: This is a broad term that encompasses all types of fuel sources and methods of powering machines.
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Sun: Solar energy can be harnessed by machines designed to use photovoltaic cells or solar thermal systems, allowing them to operate using sunlight.
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Electricity: Many machines run on electricity, but they can be powered by various sources, including renewable energy (like solar or wind) and fossil fuels (like coal or natural gas) when converted to electricity.
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Gasoline: Many types of machines, such as internal combustion engines in cars and small engines in lawn equipment, are specifically designed to run on gasoline.
In summary, machines can be powered by a variety of energy sources, including electricity, gasoline, and renewable sources like solar energy. Therefore, the best answer would be Energy, as it encompasses all possible fuel sources.