Answer:
The weight of the air
Step-by-step explanation:
The atmosphere is made of gases, these gases are matter and matter has mass, this mass under the influence of gravitational pull towards the center of the earth (gravity) and a large number of molecules in all the atmosphere's layers become weight which exerts pressure, atmospheric pressure. This atmospheric pressure is modified by the planetary rotation and local effects such as wind velocity, density variations due to temperature and variations in composition.
Therefore, we can conclude that atmospheric pressure is caused by the weight of the air.
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