**Core Concept**
Gallstones are solid particles formed in the gallbladder, and their composition can vary, affecting their radio-opacity. Understanding the types of gallstones and their characteristics is crucial for diagnosis and management.

**Why the Correct Answer is Right**
Gallstones can be classified into cholesterol stones, pigment stones, and mixed stones. Cholesterol stones are the most common type in Western populations, while pigment stones are more common in Asian populations. The radio-opacity of gallstones depends on their composition, with cholesterol stones being radiolucent (not visible on X-rays) and pigment stones being radio-opaque. Therefore, stating that 90% of GB stones are radio-opaque is incorrect.

**Why Each Wrong Option is Incorrect**
**Option A:** Mixed stones are indeed common in the West, particularly in regions with a high prevalence of cholesterol stones. This option is correct, not incorrect.

**Option B:** Saint's Triad refers to a condition characterized by gallstones, diverticulosis of the colon, and hiatus hernia. This option is correct, not incorrect.

**Option C:** A history of gallstones is a known risk factor for the development of gallbladder carcinoma. This option is correct, not incorrect.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the composition of gallstones can vary significantly between different populations. Cholesterol stones are more common in Western populations, while pigment stones are more common in Asian populations. This knowledge can help clinicians tailor their diagnostic approach to the specific population being evaluated.

**Correct Answer Line**
✓ Correct Answer: D. 90% of GB stones are radioopaque