What defines the atmospheric pressure in a high-pressure system?

A high-pressure system is primarily characterized by descending air, which plays a significant role in promoting fair weather conditions. As air descends, it undergoes compression and warming, leading to the evaporation of moisture and the inhibition of cloud formation. This is why high-pressure systems are often associated with clear skies, sunshine, and stable weather, making them conducive to pleasant atmospheric conditions.

The other aspects mentioned in the choices can be associated with low-pressure systems or other atmospheric phenomena. For example, rising air tends to occur in low-pressure systems, leading to cloud formation and potentially stormy weather, which contrasts with the characteristics of a high-pressure system. Additionally, while high-pressure systems might have air movement, the specific hallmark of a high-pressure system is the descending air that results in the stability of the atmosphere rather than turbulence.