Final answer:
Loperamide is the anti-diarrheal medication among the options given. It is used to reduce bowel movements and watery stool. Alosetron is also for diarrhea but specifically for severe IBS in women.
Step-by-step explanation:
Out of the options provided, A) Loperamide is a medication that is used as an anti-diarrheal. It works by slowing down the movement of the gut, which helps reduce the frequency of bowel movements and makes stool less watery. D) Alosetron (Lotronex), however, is used specifically for severe diarrhoea-predominant irritable bowel syndrome (IBS) in women, but its use is limited due to potential serious side effects. Conversely, B) Tetracycline is an antibiotic that treats bacterial infections and C) Sucralfate is used to treat ulcers in the digestive system.