Heated Air Masses Above the Equator Move North and South

Heated air masses above the equator move north and south to cooler areas because:

A) The equator spins faster than the polar regions as Earth rotates.
B) Cooler areas of air are less dense.
C) Rotational gravity pulls the air north and south.
D) The moon exerts a gravitational pull on the air.
E) The sun exerts a gravitational pull on the air.