Fact 1: Cartilage is a tough tissue that contains a protein called collagen.

Fact 2: Collagen contributes to meat toughness.

Given the two facts above, answer the question "what contributes to meat toughness?" with the following options: 
- digestion
 - cartilage
 - layers of fat
 - h2o
 - exercise
 - Animal fur
 - the skin
 - steak


 

  cartilage       