A narrow region between two air masses of different densities is a

A. gulley.

B. ridge.

C. front.

D. system.

A weather front or front is a narrow region between two air masses of different densities. The answer is letter C. Because of the difference in density between warm and cold front, cold air tends to go underneath the warmer air. It often creates the strongest winds above the ground surface. This is caused due to the heat and mass transfer between particles of air. They can be slowed down by the presence of mountains and valleys. Cold air moves fast and the temperature around it can be felt as if you are blown away due to its density. Whereas warm air moves slowly.

A narrow region between to air masses of different densities is a C. front.