What environmental condition causes cold air to move toward hot air?

The correct choice is higher pressure gradients. This is because cold air tends to be denser and heavier than warm air. When there is a higher pressure gradient, it indicates a significant difference in atmospheric pressure between two areas. Such a difference will naturally cause the denser, cooler air to move toward areas of lower pressure, where the air is warmer. This principle of air movement driven by pressure differences is fundamental in meteorology and helps explain wind patterns and weather changes.

Higher pressure systems often lead to descending air, which can stabilize the atmosphere, whereas lower pressure systems typically encourage uplifting and the formation of clouds and precipitation. Higher humidity levels are more related to moisture content in the air rather than temperature differences driving air movement. Temperature inversions occur when warmer air traps cooler air near the surface, which can lead to a lack of vertical mixing, but they don't describe the movement of cold air toward hot air in the context of pressure gradients.