The three circulation cells that occur either side of the equator (such as the hadley cell) are caused by:

select one:

a. el niño - southern oscillation

b. the earth's rotation and the coriolis effect

c. the thermohaline circulation

d. oceanic salinity gradients

e. subtropical gyres

The correct answer is b.

Explanation:

The three circulation cells that occur either side of the equator (such as the Hadley cell) are caused by The Earth's rotation and the Coriolis effect.

This is because the Earth rotates from West to East, (counterclockwise), the rotation speed is lower at the poles than in Ecuador.

Due to Coriolis forces any fluid that travels horizontally on the Earth's surface tends to deviate to the right in the Northern hemisphere and to the left in the Southern hemisphere.

This force appears when a body is in motion with respect to a rotating system. It is always perpendicular to the direction of the system's axis of rotation and the direction of body movement seen from the system in rotation.