**Core Concept**
Gastric ulcers are mucosal breaks in the stomach lining, often resulting from an imbalance between mucosal defense and aggressive factors such as acid-pepsin secretion. Refractory ulcers fail to heal despite adequate treatment, indicating an underlying issue that needs to be addressed.

**Why the Correct Answer is Right**
The correct answer is 8 weeks of therapy. This is because the healing of gastric ulcers is typically assessed after 8 weeks of treatment with proton pump inhibitors (PPIs) or other acid-suppressing medications. If an ulcer fails to heal after this time, it is considered refractory, and further evaluation is necessary to identify the underlying cause.

**Why Each Wrong Option is Incorrect**
**Option A:** 4 weeks is too early to assess healing, as gastric ulcers may take several weeks to respond to treatment.
**Option B:** 12 weeks is too long, as prolonged use of acid-suppressing medications can lead to complications such as osteoporosis and Clostridioides difficile infection.
**Option C:** 2 weeks is not sufficient time for the ulcer to heal, as the mucosal repair process can take several weeks.

**Clinical Pearl / High-Yield Fact**
Refractory ulcers can be caused by factors such as Helicobacter pylori infection, use of nonsteroidal anti-inflammatory drugs (NSAIDs), and underlying conditions like Zollinger-Ellison syndrome. It's essential to consider these factors when evaluating a patient with a refractory gastric ulcer.

**Correct Answer: C. 8 weeks of therapy.**