You are presented with the quiz "porcupine can use its quills as a what" 

But you don't know the answer, so you turn to your teacher to ask for hints. He says that "threatening behavior by predators causes a porcupine to extend its quills" and "porcupines only inflate and extend their spines as a defense mechanism". 

So, what's the best answer to the question?


 

   defense mechanism        