Which front is described as a composite of warm, cool, and cold fronts and forms around low-pressure systems?

• A. A front where warm air moves over cold air mass.
• B. The boundary between two air masses.
• C. Composite of warm, cool, and cold fronts; forms around low-pressure systems.
• D. A front that advances behind a warm front.

Answer: (C)

Occluded front. In a mature low-pressure system, a cold front can catch up to a warm front. As the cold air overtakes, the warm air is lifted off the surface, and the boundary becomes a single front that contains air masses with characteristics of warm, cool, and cold air. This mixing around the cyclone is what defines an occluded front, which forms specifically around low-pressure systems.

The other descriptions describe simpler fronts: a warm front is warm air sliding over cooler air; a general boundary between air masses is just a front without the composite structure; and a front that advances behind a warm front describes a typical cold front but not the occluded, multi-mass arrangement.