**Core Concept**
The investigation of choice for suspected gallbladder stones involves imaging studies that can accurately visualize the gallbladder and its contents. The ideal investigation should be non-invasive, cost-effective, and provide high-quality images to aid in diagnosis.

**Why the Correct Answer is Right**
The correct investigation of choice is the **Transabdominal Ultrasound (USG)**. Ultrasound is a non-invasive, radiation-free imaging modality that uses high-frequency sound waves to produce images of the internal organs. It is particularly effective in visualizing the gallbladder and detecting gallstones, inflammation, and other abnormalities. The ultrasound waves can penetrate the abdominal wall and provide detailed images of the gallbladder, making it an ideal investigation for suspected gallbladder stones.

**Why Each Wrong Option is Incorrect**
**Option A:** **Intravenous Cholangiography (IVC)** is not the investigation of choice for suspected gallbladder stones. IVC involves injecting a contrast agent into the bloodstream, which is then excreted by the liver and biliary system. While it can provide images of the biliary system, it is not as sensitive as ultrasound for detecting gallstones.

**Option B:** **Magnetic Resonance Cholangiopancreatography (MRCP)** is a highly sensitive imaging modality for visualizing the biliary and pancreatic ducts. However, it is more expensive and less widely available than ultrasound, making it a second-line investigation for suspected gallbladder stones.

**Option C:** **Endoscopic Retrograde Cholangiopancreatography (ERCP)** is a minimally invasive procedure that involves inserting an endoscope into the stomach and duodenum to visualize the biliary and pancreatic ducts. While it can provide detailed images and allow for therapeutic interventions, it is not typically used as a first-line investigation for suspected gallbladder stones.

**Clinical Pearl / High-Yield Fact**
Ultrasound is the investigation of choice for suspected gallbladder stones due to its non-invasive nature, high sensitivity, and wide availability. It is often the first imaging modality used in patients with suspected gallstones, and it can provide a definitive diagnosis in many cases.

**Correct Answer: C. Endoscopic Retrograde Cholangiopancreatography (ERCP)**