You are presented with the question "What has skeleton made of tough tissue that contains a protein called collagen?" and the following answer choices: 
- mammals
 - rocks
 - animals
 - sharks
 - a fish
 - cows
 - humans
 - plants

Now knowing that cartilage is a tough tissue that contains a protein called collagen and sharks have a cartilage skeleton, choose the best answer.


 

    sharks     