The phases of the moon are caused by
a) the moon revolving around the sun and earth.
b) earth revolving around the sun and the sun's light being reflect off the moon.
c) the moon revolving around earth and the moon reflecting sunlight towards earth.
d) the moon revolving around earth with sunlight reflecting off of earth towards the moon.

The lunar phases are produced as a result of the change of the relative positions of the Earth, the Moon and the Sun.

The part of the lunar surface illuminated by the Sun that we can see from the Earth, is changing throughout a cycle that is repeated periodically every 29 days, 12 hours, 43 minutes and 12 seconds.

The answer is: B) Earth that revolving around the sun and the sun's light being reflected off the moon.