## **Core Concept**
Helicobacter pylori (H. pylori) infection is a significant factor in the pathogenesis of gastric ulcers. The bacterium causes chronic gastritis, which can lead to gastric ulceration. The incidence of H. pylori infection in patients with gastric ulcers is notably high.

## **Why the Correct Answer is Right**
The correct answer, **C. 70-90%**, reflects the established medical understanding that a significant majority of gastric ulcers are associated with H. pylori infection. This bacterium disrupts the gastric mucosa's protective mechanisms, leading to ulcer formation. Studies have consistently shown that eradicating H. pylori infection can lead to the healing of gastric ulcers and reduce the risk of recurrence.

## **Why Each Wrong Option is Incorrect**
- **Option A:** 10-30% - This option underestimates the incidence of H. pylori in gastric ulcers. The actual association is much higher than this range.
- **Option B:** 40-50% - Although this range might seem plausible, it still underrepresents the strong link between H. pylori infection and gastric ulcers.
- **Option D:** 90-100% - This option overestimates the incidence. While H. pylori infection is a major cause, not all gastric ulcers are attributed to this bacterium; other factors like NSAID use also play a significant role.

## **Clinical Pearl / High-Yield Fact**
A crucial point to remember is that the presence of H. pylori infection in gastric ulcers is a key factor for targeted therapy. The test-and-treat strategy for H. pylori is recommended in many guidelines for patients with gastric ulcers, highlighting the importance of identifying and treating this infection.

## **Correct Answer:** C. 70-90%.