**Core Concept**
Hemobilia refers to the presence of blood in the bile or bile ducts, often resulting from a traumatic or iatrogenic injury to the bile ducts or gallbladder. The condition can be caused by various factors, including surgical complications, gallstones, or tumors.

**Why the Correct Answer is Right**
The most common cause of hemobilia is iatrogenic trauma to the bile ducts, often resulting from liver biopsies or endoscopic retrograde cholangiopancreatography (ERCP) procedures. These procedures can cause mechanical injury to the bile ducts, leading to bleeding. The bleeding can arise from the erosion of blood vessels in the bile duct wall or from the disruption of the mucosal lining of the bile ducts.

**Why Each Wrong Option is Incorrect**
* **Option A:** Traumatic injury to the gallbladder is a possible cause of hemobilia, but it is less common than iatrogenic trauma.
* **Option B:** Gallstones are a common cause of biliary obstruction and pain, but they are not typically associated with hemobilia.
* **Option C:** Liver tumors can cause hemobilia, but they are a less common cause compared to iatrogenic trauma.

**Clinical Pearl / High-Yield Fact**
It is essential for clinicians to be aware of the potential for bleeding during liver biopsies or ERCP procedures and to take measures to prevent or manage hemobilia if it occurs.

**Correct Answer: C. Liver tumors.