Question 1272Navigation General

The correct answer is C) a warm air mass rising over a cold air mass. This is correct because the rising of a warm air mass over a cold air mass is the primary mechanism that causes the formation of a frontal thunderstorm. As the warm air rises, it cools, and the moisture in the air condenses, leading to the development of towering cumulonimbus clouds and the potential for thunderstorm activity along the frontal boundary. The other options are incorrect because they do not directly relate to the formation of a frontal thunderstorm. Option A describes a process that can lead to the development of thunderstorms in general, but not specifically frontal thunderstorms. Option B describes a mechanism for mountain-induced thunderstorms, and option D refers to local heating, which is more associated with the formation of convective thunderstorms rather than frontal storms.