The correct answer is D. They both have an alternating arrangement of glucose molecules, but cellulose has hydrogen bonds while chitin has amino group bonds.
Chitin and celulose are hard to digest because THEY BOTH HAVE AN ALTERNATING ARRANGEMENT OF GLUCOSE MOLECULES, HOWEVER CELLULOSE HAVE HYDROGEN BONDS WHILE CHITIN HAS AMINO GROUP BONDS. Humans does not have enzymes that can break the beta acetal linkages that are present in cellulose, thus they can not digest cellulose.
