Which of the following best describes a high-pressure system?

A high-pressure system is characterized by air that sinks, which typically results in stable atmospheric conditions. As the air descends, it compresses and warms, leading to the formation of clear skies. This downward movement inhibits the development of clouds and precipitation, providing the typical weather associated with high-pressure systems, which is clear and calm.

Clouds and precipitation are more commonly associated with low-pressure systems, where rising air leads to cooling and condensation. While low humidity and calm winds can occur, they do not fully capture the essence of high-pressure systems, as these systems are more about the stability and sinking of air. Warm air that holds moisture is relevant to weather patterns but is more indicative of low-pressure systems where convection can lead to cloud formation and rain. Hence, the feature of sinking air and the resulting clear skies is what best defines a high-pressure system.