What weather-related characteristic commonly occurs under high-pressure systems?

High-pressure systems are typically associated with descending air, which inhibits cloud formation and leads to stable atmospheric conditions. When air descends, it warms, creating conditions that suppress moisture and cloud development. This results in clear or cloudless skies, allowing for more sunlight to reach the surface.

In contrast, widespread thunderstorms are more commonly associated with low-pressure systems, where rising air creates instability and allows for moisture to condense and form clouds. Heavy cloud formations also tend to occur under low-pressure systems, which can generate precipitation and storm activity. High humidity levels can be present with certain weather patterns, but in a high-pressure system, the descending air tends to reduce humidity, contributing instead to dry conditions. Therefore, clear or cloudless skies are the hallmark of high-pressure systems, making this the correct choice.