Which of the following air mass classifications is based on moisture content?

a. tropical
b. arctic
c. polar
d. maritime

Option (D)

Explanation:

Maritime tropical type of air masses generates over the warmer oceanic water of the tropical areas and the region of Gulf of Mexico. This tropical areas are rich in moisture content, from where the heat and moisture are transferred from the ocean surface water to the overlying air masses. These air masses then moves towards the northern side carries the warm and moist air into the regions of United States, which eventually leads to the occurrence of precipitation.

This air mass is classified based on the moisture content.

Thus, the correct answer is option (D).