Fact 1: Nuclear reactions in stars causes stars to produce light.

Fact 2: And, of course, the Sun is a star.

Given the two facts above, answer the question "What in the sun causes the sun to produce light?" with the following options: 
- energy of moving objects
 - hydrogen and oxygen
 - heat energy
 - water
 - solar rays
 - rotation
 - nuclear reactions
 - kinetic energy


 

       nuclear reactions  