Answer:
Air pressure is caused by the gravity of the earth.
Step-by-step explanation:
Air pressure is the force exerted by air; whether compressed or unconfined, on any surface in contact with it.
Air pressure is the weight of particles of gases as pressed down by gravity while mainting it's relative and variable equidistant matrix. Artificial pressure can be increased by chamber and piston pumping action or reduce by vacuuming.