**Core Concept**
The question targets the understanding of different pharmacological mechanisms of anti-ulcer drugs, specifically those that do not involve reducing gastric acid secretion or neutralization. Anti-ulcer drugs work by various mechanisms, including reducing acid secretion, neutralizing acid, protecting the mucosa, or promoting healing.

**Why the Correct Answer is Right**
To approach this question, let's analyze the mechanisms of the given options. Most anti-ulcer medications work by either reducing gastric acid secretion through histamine antagonism (H2 blockers), direct acid neutralization (antacids), or mucosal protection (sucralfate). However, some medications work through other mechanisms such as promoting healing or altering the gastric pH through other means. For example, prostaglandin analogs like misoprostol protect the gastric mucosa by promoting prostaglandin synthesis, which helps in protecting the mucosa from acid.

**Why Each Wrong Option is Incorrect**
**Option A:** H2 blockers (e.g., ranitidine) act by reducing gastric acid secretion through histamine antagonism at the H2 receptors on the parietal cells. This mechanism directly affects acid production.
**Option B:** Antacids (e.g., aluminum hydroxide) neutralize gastric acid by increasing the pH of the stomach contents, which directly affects acid concentration.
**Option C:** Proton pump inhibitors (PPIs) like omeprazole reduce gastric acid secretion by irreversibly inhibiting the H+/K+ ATPase (proton pump) on the parietal cells, thereby reducing acid production.

**Clinical Pearl / High-Yield Fact**
It is essential to remember that different classes of anti-ulcer medications have distinct mechanisms of action, and understanding these differences is crucial for effective management of peptic ulcer disease.

**Correct Answer:** D.