Solar energy involves the most dangerous equipment. Solar energy requires the most complicated technology. The supply of solar energy will not change for billions of years. The supply of solar energy causes it to be the cheapest kind of energy.
I gave my students this multiple choice question: What makes solar energy different from most other energy that people use?

Only one answer is correct among these 4 choices:
- Solar energy involves the most dangerous equipment.
- Solar energy requires the most complicated technology.
- The supply of solar energy will not change for billions of years.
- The supply of solar energy causes it to be the cheapest kind of energy.

Could you tell me which one is correct?

The supply of solar energy will not change for billions of years.