Fact 1: Threatening behavior by predators causes a porcupine to extend its quills.

Fact 2: Similarly, threatening or intimidating behaviors are also forbidden.

Given the two facts above, answer the question "What defense mechanism does a porcupine use when intimidated?" with the following options: 
- eardrum
 - deadly
 - sound
 - instincts
 - steroids
 - organ
 - quills
 - blastoids


 

       quills  