Answer the following question given this paragraph: 

The Sun is Earth’s main source of energy. The Sun gives us both light and heat. The Sun changes hydrogen into helium through nuclear fusion. This releases huge amounts of energy. The energy travels to the Earth mostly as visible light. The energy is carried through the empty space by radiation . We can use sunlight as an energy resource, called solar energy ( Figure above ).


Q: What is earth's main source of energy?

 Choices:

- the atmosphere

- the moon

- the core

- the sun

A:
the sun
