Which statement about occluded fronts is true?

• A. They form when warm air moves over cold air
• B. They form when two high-pressure systems meet
• C. They form when a cold front catches up to a warm front
• D. They form only over land

Answer: (C)

Occluded fronts occur when a cold front catches up to a warm front within a mid-latitude cyclone, lifting the warm air that lies between them off the surface and forming a single, extended boundary. This overtaking process is what defines an occlusion. Once the cold front overtakes the warm front, the surface boundary becomes the occluded front, and the weather along and near that boundary often includes widespread or persistent precipitation as the warm, moist air is forced upward.

This description matches the statement that the cold front catches up to the warm front. The alternative that warm air moves over cold air describes a warm front, not an occlusion. The idea of two high‑pressure systems meeting doesn’t involve fronts or occlusions, which arise in a developing low‑pressure cyclone. And occlusions aren’t limited to land; they can form over water as the cyclone moves and evolves.