A patient is using psyllium hydrophilic mucilloid (Metamucil) to promote evacuation of stool. What is the action of this bulk-forming laxative?
A) It reduces the surface tension of bowel contents.
B) It irritates the intestinal mucosa, thus increasing intestinal motility.
C) It increases mass and water content of stool, promoting evacuation.
D) It creates a barrier between the colon wall and feces.