In a healthy person, the feces leaving the body contain very few undigested molecules from food. one major exception is cellulose, which leaves the body virtually intact. from this we can conclude that the human digestive system does not
answer
contain enzymes that can digest proteins such as cellulose.
digest cellulose because it does not contain any energy.
have a large intestine long enough to break down cellulose.
produce enzymes that can break down cellulose.