Final answer:
Stimulating the parasympathetic system does not treat acid reflux; it actually can exacerbate digestive activity. Antacids, histamine-receptor blockers, and proton pump inhibitors are effective treatments that help manage acid reflux by reducing stomach acid production.
Step-by-step explanation:
The substance in option d, stimulating the parasympathetic system, does NOT reduce the symptoms of, or treat, acid reflux.
The parasympathetic system is part of the autonomic nervous system, and when stimulated, it promotes digestive activity, which is not conducive to alleviating acid reflux symptoms.
In contrast, antacids (a), histamine-receptor blockers (b), and proton pump inhibitors (c), are all treatments that help manage acid reflux.
Antacids neutralize excess acid in the stomach, and drugs like H₂-receptor antagonists or proton pump inhibitors reduce the production of stomach acid.