Maritime air masses are formed over what type of environment?

Maritime air masses are indeed formed over large bodies of water, notably oceans. This environment is crucial because the characteristics of the air mass are influenced by the water's temperature and evaporation rates. When air sits over a warm ocean, it absorbs moisture, leading to a humid air mass that can contribute to precipitation when it moves over land. These air masses are typically more stable and can carry moisture to different regions, impacting weather patterns significantly.

In contrast to the other environments listed, which include mountains, land, and deserts, maritime regions are unique because they provide the necessary moisture that defines maritime air masses. Mountains can create orographic lift but are not a source of moisture in the same way. Land areas can lead to continental air masses that are generally drier, and deserts have extremely low humidity, which does not support the formation of moist air masses. Thus, the correct answer highlights the essential role that water bodies play in the formation of maritime air masses.