Here's a problem to solve: Anne's project for the science fair is about renewable energy. She wants to describe an activity that uses a renewable source of energy. Which activity should she describe in her project?

Among the 4 following options, which is the correct answer?

- A: fueling a car with gas
 
- B: heating a house with oil
 
- C: flying a kite in the wind
 
- D: grilling food over charcoal
 