What does a squall line consist of?

A squall line is a type of weather phenomenon that consists of a line of severe thunderstorms that typically develop along or ahead of a cold front. These storms are characterized by a rapid increase in wind speed, heavy rainfall, and often severe weather conditions such as hail or tornadoes.

The formation of squall lines is primarily associated with the lifting of warm, moist air over a cold front, which leads to vigorous convection and storm development. The storms can produce strong straight-line winds, hence the term "squall."

By understanding that squall lines are linked specifically to cold fronts, it becomes clear why the correct option highlights storms forming on a cold front, distinguishing them from other weather phenomena associated with different types of fronts, like waterspouts or clouds that are not specifically indicative of the squall line formation.