Detailed Instructions: You will be given a trivia clue, and the category it belongs to. You should answer with the best answer that belongs in the category and is described by the clue. For simplicity, answers should be in all lower cased letters.
Problem:Category: SUN 
Clue: In the main reaction making the sun's energy, 2 of these nuclear particles fuse & one becomes a neutron
Solution:
protons