A 45-year-old man presents with a 3-month history of retrosternal burning pain that awakens him at night and worsens 30–60 minutes after eating spicy foods or large meals. He denies dysphagia, weight loss, or melena. Vital signs are normal. Upper endoscopy shows erythematous mucosa in the distal esophagus without ulceration or Barrett's changes. A diagnosis of erosive GERD is made, and omeprazole 20 mg daily is initiated. The patient experiences symptom resolution within 2 weeks. Which of the following best explains the mechanism by which omeprazole provides therapeutic benefit in this patient?

1. A)Competitive antagonism of histamine-2 receptors on gastric parietal cells, reducing basal and stimulated acid secretion
2. B)Irreversible inhibition of the H+/K+-ATPase pump on the apical membrane of parietal cells, suppressing acid secretion for 24–48 hoursGABARITO
3. C)Coating of the gastric mucosa with a protective bicarbonate layer that neutralizes residual acid and promotes mucosal healing
4. D)Nonselective inhibition of gastric proton pump isoforms including H+/K+-ATPase and V-ATPase, affecting multiple cellular compartments
5. E)Neutralization of free hydrogen ions in the gastric lumen through direct chemical reaction, increasing intragastric pH to >4