Final answer:
The type of diarrhea that is not a recognized category is diffusion diarrhea. Recognized types include motility-related, secretory, and inflammatory diarrhea.
Step-by-step explanation:
The type of diarrhea that is NOT an actual category is C. diffusion diarrhea. The recognized types of diarrhea include motility-related diarrhea, which is due to increased movement in the gastrointestinal tract; secretory diarrhea, caused by the secretion of water and electrolytes into the intestine; and inflammatory diarrhea, associated with diseases like Crohn's disease and ulcerative colitis, where the intestinal lining is inflamed and unable to absorb nutrients properly.