Shivering occurs when many muscles contract a little bit all at once, and almost all birds use shivering as a short term adjustment to the cold. Given these facts, what can contract a little bit all at once as a short term adjustment to the cold among the following options:
- that metal
 - muscles
 - Weight
 - stomach
 - mammals
 - atoms
 - ligaments
 - sweating


 

  muscles       