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?

  Options: 
 A. the wind blowing against the tires
 B. the air escaping from the spinning tires
 C. the rubbing between the ground and the tires
 D. the heat transferring from the rider's hands to the tire
Answer: C