Explain why the moon’s revolution and rotation cause the same side of the moon to always face earth.

There are a few different reasons why the Moon's revolution and rotation cause the same side of the Moon to always face the Earth. 

A few of the reasons are:

The moon spins only once during a revolution 
Both motions are completed in approximately  27.3 days. 
The moon rotates at the at the same rate it revolves around the moon. 

Any of these answers are acceptable answers to the question you asked.