Where do continental air masses typically form?

Continental air masses typically form over large land areas where the air can become relatively stable in temperature and humidity. These regions may include deserts or plains which contribute to the characteristics of the air mass. In such areas, the surface absorbs solar energy and influences the air above it, leading to the formation of air masses that are generally dry and defined by their temperature, being either warm or cold.

In contrast, air masses that form over large bodies of water tend to be more humid and are classified as maritime air masses. Urban areas generally do not provide the extensive, uniform land surface required for the consistent formation of air masses, and mountain ranges create barriers that can disrupt the flow and characteristics of air masses rather than serve as regions of formation. Thus, large land areas are crucial for the development of continental air masses, which is why this answer is correct.