Answer:
The answers are generate light, generate heat, fuse atoms of hydrogen to make helium atoms. That other answer over there didn't select all that apply, because they have a dumb stinky brain.
Step-by-step explanation:
The main source of heat on earth is the sun. The sun is made mostly of hydrogen and helium. Nuclear reactions within the sun change hydrogen atoms into helium atoms. This process releases a tremendous amount of energy in the form of heat and light.