**Core Concept**
The question is testing the understanding of the imaging modalities used in the gastrointestinal (GI) tract, specifically the choice of contrast agent for Oral Cholecystography (OCG). OCG is a radiological examination of the gallbladder and bile ducts using a contrast agent that is taken orally.

**Why the Correct Answer is Right**
The correct answer is **Iodipamide**. Iodipamide is a water-soluble, non-ionic contrast agent that is taken orally and then absorbed into the bloodstream, from which it is transported to the liver and eventually to the gallbladder. It is used for OCG because it is well-tolerated and provides a clear image of the gallbladder and bile ducts.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not a commonly used contrast agent for OCG.
* **Option B:** This option is not relevant to OCG, as it is not a contrast agent used for this purpose.
* **Option D:** This option is not the correct answer, as it is not a commonly used contrast agent for OCG.

**Clinical Pearl / High-Yield Fact**
It's worth noting that OCG is not as commonly used today as it was in the past, due to the advancement of other imaging modalities such as ultrasound and CT scans.

**Correct Answer: C. Iodipamide**