Fact 1: The moon revolving around the Earth causes the phases of the moon.

Fact 2: Phases of the moon, however, depend on the relative positions of the Earth, moon, and Sun.

Given the two facts above, answer the question "what do moon phases depend on?" with the following options: 
- heat
 - UV
 - RNA
 - stars
 - tides
 - asteroids
 - sun
 - mass


 

       sun  