This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Gastro-Intestinal Tract, Subject name: Pharmacology
A small amount of atropine is added to diphenoxylate in order to: 
Select and explain. 
A. Suppress associated vomiting of gastroenteritis, B. Augment the anti-motility action of diphenoxylate, C. Block side effects of diphenoxylate, D. Discourage overdose and abuse of diphenoxylate
D: Discourage overdose and abuse of diphenoxylate
Answer: D: Discourage overdose and abuse of diphenoxylate 
Explanation: Atropine is intentionally added to diphenoxylate in fixed dose combinations to intentionally produce the adverse effects. - If the person takes diphenoxylate in large doses to get the euphoria, atropine will produce adverse effects and the person will not abuse the drug.