Energy.

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Across
  1. 2. Natural ___. Found in fossil fuels.
  2. 4. Humans eat this to obtain energy.
  3. 6. Salt is a ________.
  4. 7. There are many types of ______.
  5. 8. Electricity supply.
  6. 9. This keeps us warm.
Down
  1. 1. Used as a source of power.
  2. 3. We burn ____ to produce heat.
  3. 5. The ___ produces food for plants.
  4. 6. A flow of electricity.