Explanation:
Concept overview / definition
Key idea: Atmospheric pressure is the pressure produced by the weight of the air above a surface.
It is defined using the idea of an air column resting on a unit area, so gravity and the mass of air matter.
Why the correct option is correct
The correct option matches the standard definition: pressure equals force per unit area, and here the force comes from the weight of the air column above that area.
This definition stays valid whether you imagine the column above your head or above any fixed surface at a given level.
Why the other options are incorrect
Options that describe only “presence of air”, “humidity”, or “wind speed” confuse pressure with other atmospheric properties.
Options that mention only temperature are incomplete because temperature can influence pressure indirectly, but it is not the definition of pressure itself.
UPSC exam tip / common confusion
Elimination: If an option does not mention both air column (mass/weight) and unit area, it is usually not a definition.
Also remember: pressure is a scalar and can be expressed in multiple units without changing the concept.
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