Final answer:
The pathogen that uses its motility to follow a chemo-tactic gradient and attaches to the intestinal mucosa without penetration is Vibrio cholerae, the causative agent of cholera.
Step-by-step explanation:
The pathogen in question is identified by its motility and behavior of attaching to, but not penetrating, the intestinal mucosa. The correct answer to the question is A) Vibrio cholerae. V. cholerae is a curved rod-shaped, gram-negative bacterium capable of motility. It is known for causing the severe diarrheal illness cholera. This bacterium moves along a chemo-tactic gradient in the intestines, adheres to the intestinal mucosal epithelial cells, and produces cholera toxin. The toxin induces an increase in cAMP levels in the intestinal cells, which results in excess secretion of chloride ions and water into the gut lumen, causing an electrolyte imbalance and the characteristic profuse 'rice-water stool' diarrhea seen in cholera patients.