Humans Are Not Able to Digest Cellulose as a Food

Multiple Choice

Humans are not able to digest cellulose as a food source because:

A) Cellulose is very insoluble.
B) It is more important that the cellulose is used as fiber in our bodies.
C) We lack the enzyme to break the β linkage in the cellulose.
D) Cellulose is insoluble and we lack the enzyme to break the β linkage in the cellulose.
E) All of these are reasons why we cannot digest cellulose.