friction from the air heat being absorbed from the sun mechanical energy being absorbed energy conversions occurring in her body
I gave my students this multiple choice question: Ana is a cross-country runner. After finishing a race she noticed that she felt hot due to the release of thermal energy. Which is the most likely source of the thermal energy?

Only one answer is correct among these 4 choices:
- friction from the air
- heat being absorbed from the sun
- mechanical energy being absorbed
- energy conversions occurring in her body

Could you tell me which one is correct?

energy conversions occurring in her body