How many "cells" of circulating air are found around the earth? 9 6 3 12?

There are six cells of circulating air found around the earth,
Global circulation is the world-wide system of winds by which necessary transfer of heat from tropical to polar latitudes is accomplished. In each hemisphere; that is; the northern and southern hemisphere, there are three cells , that is the Hadley cell, Ferrel cell and Polar cell, in which air circulates through the entire depth of the troposhere. 

Plants take energy from the sunlight with the of chlorophyll so the plant starts the food chain. then an herbivore eats the plant and gets its energy.then a carnivore or a human eats the herbivore and gets its energy. : )

Im like 95% sure the answer is b