Here's a problem to solve: The human body temperature is relatively constant. Which is a feedback mechanism that helps the human body maintain its normal temperature in a cold environment?

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

- A: Water is released from the skin.
 
- B: Muscles shake in small movements.
 
- C: The rate of heart beats slows.
 
- D: The lungs take in additional air.
 