The digestive system

Hydrogen peroxide is a liquid compound composed of oxygen and hydrogen. A student fills each of two test tubes half full of hydrogen peroxide and notices no reaction occurs in either tube. When she adds a small piece of fresh liver to one of the test tubes, she observes a great deal of bubbling in that tube. A test shows that the bubbles escaping are oxygen gas. The piece of liver must contain


1. The substrate in this reaction is
 
a) hydrogen peroxide.

 
b) oxygen.

 
c) liver.

 
d) hydrogen.

I think the awnser is c but im, not sure.


2.The fact that oxygen was given off indicates that
 
a) the liver was chemically changed.

 
b) co-enzymes were produced during the reaction.

 
c) an enzyme was consumed during the reaction.

 
d) hydrogen peroxide was chemically changed

I think the answer is d