Physics
The law of conservation of energy states that

Energy can either be created nor destroyed
Energy can either be created or destroyed
Energy can neither be created nor destroyed
Energy can neither be created or destroyed

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Physics
It takes much longer to cook food in the hills than in the plains, because

in the hills the humidity is high and therefore a lot of heat is absorbed by the atmosphere leaving very little heat for cooking
due to low atmospheric pressure on the hills, the water boils at a temperature higher than 100oC and therefore water takes longer to boil
in the hills the atmospheric density is low and therefore a lot of heat is lost to the atmosphere
n the hills the atmospheric pressure is lower than that in the plains and therefore water boils at a temperature lower than 100oC causing an increase in cooking time

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