You are presented with the question "porcupine can use its quills as a what" and the following answer choices: 
- encoded information
 - threatened
 - defense mechanism
 - cushion
 - protective bony armor
 - cleaning mechanism
 - if humans disturb bears
 - brush

Now knowing that threatening behavior by predators causes a porcupine to extend its quills and porcupines only inflate and extend their spines as a defense mechanism, choose the best answer.


 

   defense mechanism      