Final answer:
The formation of subtropical deserts is primarily due to atmospheric convection cells that create high-pressure systems with descending dry air, forming arid conditions typical of regions such as the Sahara and the Namib deserts.
Step-by-step explanation:
The primary factor responsible for the formation of subtropical deserts is a. Atmospheric convection cells. These are large-scale patterns in the atmosphere that contribute to the climate characteristics of different regions. Subtropical deserts, such as the Sahara and the Namib, experience high-pressure systems and descending dry air, leading to arid conditions. These deserts are situated between 15° and 30° north and south of the equator, often on the lee side of mountain ranges, which create a rain shadow effect further contributing to desert formation.
Ocean currents can influence desert conditions, but they are not the primary cause. Interactions with mountain ranges do play a role in desert formation through the rain shadow effect, while southerly winds are not generally responsible. Therefore, Atmospheric convection cells are primarily responsible for the dry and hot climate that characterizes subtropical deserts.