Final answer:
The boundary between two different air masses is referred to as C) front, being the transition zone between two distinct air masses and often leading to weather changes.
Step-by-step explanation:
The boundary between two different air masses is referred to as C) front. A front is an important concept in meteorology, as it is the transition zone between two distinct air masses of different densities, and with different temperatures and humidity levels. This transition often leads to significant weather phenomena such as rain or storms, especially when a cold front overtakes a warm front or vice versa. On weather maps, fronts are depicted as lines with different symbols indicating the type of front (e.g., cold, warm, or stationary).
Frontolysis is the process where a front weakens and begins to dissipate, while frontogenesis refers to the formation of a front. These terms describe different stages in the lifecycle of a front but they are not indicative of the actual boundary itself.