The Subtropics at 30 $\degree$ North and South of the Equator Are Characterized by Arid

The subtropics at 30 $\degree$ north and south of the equator are characterized by arid lands.This is primarily a result of:

A) rising hot air caused by solar heating in these zones
B) descending hot air that heats the ground
C) descending,dry air that is part of a cell that originates at the equator
D) rising cool,dry air that flows in a cell to the equator
E) polar air that flows towards the equator