You are presented with the quiz "Cartilage is a tough tissue made up of:" 

But you don't know the answer, so you turn to your teacher to ask for hints. He says that "cartilage is a tough tissue that contains a protein called collagen" and "many collagen fibrils come together and form a collagen and forma collagen fiber". 

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


 

       fibrils    