Air pressure is greatest because there are more molecules of air pushing down from

Air pressure is greatest at sea level because there are more molecules of air pushing down from above.

Explanation:

The number of air molecules above a surface determines air pressure. As the number of molecules increases, they exert more pressure on a surface, and the total atmospheric pressure increases. By contrast, if the number of molecules decreases, so too does the air pressure.

If  you plant the same crop in the same place each year  zaps nutrients from the earth and leaves soil weak and unable to support healthy plant growth. ... The effects of mono cropping on the environment are severe when pesticides and fertilizers make their way into ground water or become airborne, creating pollution.

Explanation:

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