What underlying factor differentiates a cold front from an occluded front?

The correct answer is that an occluded front is characterized by the presence of a warm front in between two cold air masses. In meteorological terms, an occluded front forms when a cold front overtakes a warm front, forcing the warm air aloft between two colder air masses. This can lead to various weather patterns, including precipitation, as the warm air rises and cools.

This differentiation is crucial because it explains how occluded fronts are formed and how they interact with surrounding air masses. In contrast, a cold front is simply the leading edge of a cooler air mass moving into an area occupied by warmer air, and it does not necessarily involve a warm front but is rather a singular feature.

The other options relate to different aspects of weather phenomena. The speed of the cold front refers to its movement across the terrain and does not uniquely define the mechanics of an occluded front. The temperature of the air masses is relevant to both types of fronts but does not differentiate an occluded front from a cold front specifically. Lastly, the length of the front in distance may vary for both types of fronts but does not serve as a defining characteristic between them.