Nonpathogenic Bacteria in the Intestinal Tract Perform All of These

Nonpathogenic bacteria in the intestinal tract perform all of these functions EXCEPT:

A) degrading undigested or unabsorbed dietary carbohydrate.
B) producing certain vitamins.
C) preventing invasion of tissues by pathogenic bacteria.
D) stimulating the production of proteins.
E) assisting in the development and maintenance of the mucosal lining.