**Core Concept**
The management of a bleeding duodenal ulcer that is unresponsive to medical therapy involves surgical intervention. The primary goal is to stop the bleeding and stabilize the patient.

**Why the Correct Answer is Right**
In a case where bleeding from a duodenal ulcer does not stop despite adequate medical management and transfusion, surgical intervention is necessary. The most appropriate surgical therapy in this scenario would involve directly addressing the source of bleeding.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because it may not directly address the bleeding site.
**Option B:** Incorrect as it might not be the most effective method to control bleeding from a duodenal ulcer.
**Option D:** Incorrect because it is too invasive for initial management of a bleeding duodenal ulcer.

**Clinical Pearl / High-Yield Fact**
In cases of severe, uncontrolled bleeding from a duodenal ulcer, prompt surgical intervention can be lifesaving. The choice of surgical procedure depends on the patient's condition and the surgeon's expertise.

**Correct Answer:** D. Undergoing a surgical oversew of the ulcer.