Physics
Water boils at a lower temperature on the hills because

There is less carbon dioxide on the hills
It is cold on the hills
There is a decrease in air pressure on the hills
There is less oxygen

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Physics
It is easier to roll a barrel full of coal tar than to pull it because

the rolling friction is much less than the sliding friction
more surface area of the barrel is in contact with the road when it is pulled
the full weight of the barrel comes into play when it is pulled
coal tar is a liquid and it flows in the barrel when it is rolled

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Physics
The velocity of sound in air

Does not depend on temperature
Increases with decrease of temperature
Decreases with increase of temperature
Decreases with decrease of temperature

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