**Core Concept**
The oral cholecystogram (OCG) is a diagnostic imaging technique used to visualize the gallbladder and bile ducts. It involves the ingestion of a radiopaque contrast agent that is absorbed by the gallbladder, allowing for visualization through X-ray imaging.

**Why the Correct Answer is Right**
The oral cholecystogram was first performed by Graham and Cole in 1942, marking the beginning of this diagnostic technique. The contrast agent used is typically iodine-based, and the standard dose is 1-2 ml/kg of body weight. The dye used in OCG is indeed telepaque, a radiopaque compound that is selectively taken up by the gallbladder, allowing for clear visualization. USG (ultrasound) has become a more widely used and preferred modality for gallbladder imaging due to its non-invasive nature and lack of ionizing radiation.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because the correct first performer of the OCG is not specified as Graham Cole, but rather Graham and Cole, who are often credited together for their work in this area.
**Option B:** Incorrect because the typical dose of telepaque used in OCG is usually 2-4 ml per gallbladder image, rather than 1 ml/kg.
**Option C:** Incorrect because, although USG has largely replaced OCG in many clinical settings, it is not entirely accurate to state that USG has completely replaced OCG.

**Clinical Pearl / High-Yield Fact**
The oral cholecystogram was a significant milestone in radiology, allowing for the first non-invasive visualization of the gallbladder. However, its use has declined with the advent of more modern imaging modalities like USG and CT scans.

**Correct Answer: D. Dye used is telepaque**