Final answer:
Misoprostol is the correct answer as it decreases gastric acid secretion; other options listed do not serve this function.
Step-by-step explanation:
Within the options provided, it is Misoprostol (Option B) that decreases gastric acid secretion. Misoprostol is a medication that both decreases acid production in the stomach and increases the production of protective mucus lining the stomach. It serves to counteract the irritating effects of nonsteroidal anti-inflammatory drugs (NSAIDs) on the stomach lining, reducing the risk of peptic ulcers in patients taking NSAIDs. On the contrary, medications such as cisapride and metoclopramide primarily work by increasing gastrointestinal motility, while sodium citrate is an antacid, which helps to neutralize existing stomach acid but does not decrease its production.