The Tropopause Altitude Is Highest Because of the

The tropopause altitude is highest because of the .

A) at the equator;air expansion from intense heating at the surface
B) at the poles;diffuse solar radiation
C) during the summer;increased atmospheric pressure
D) during the winter;Sun's direct rays hitting the Tropic of Capricorn
E) in the midlatitudes;the constant movement of the subsolar point