the wind blowing against the tires the air escaping from the spinning tires the rubbing between the ground and the tires the heat transferring from the rider's hands to the tire
I gave my students this multiple choice question: On a cold day, a student felt the tires of her bike before riding it to the store. When she arrived at the store, she felt the tires again and noticed that they were warmer. What caused the temperature of the bicycle tires to change?

Only one answer is correct among these 4 choices:
- the wind blowing against the tires
- the air escaping from the spinning tires
- the rubbing between the ground and the tires
- the heat transferring from the rider's hands to the tire

Could you tell me which one is correct?

the rubbing between the ground and the tires