**Core Concept**
The question pertains to the characteristics of gallstones in the gallbladder, a common condition that can lead to gallbladder inflammation (cholecystitis) or obstruction of the bile ducts. Gallstones are composed of various substances, including cholesterol, bilirubin, and calcium salts.

**Why the Correct Answer is Right**
Cholesterol stones are the most common type of gallstone and are formed when bile contains excess cholesterol, which precipitates out of solution and forms a solid crystal. This process is facilitated by low bile salt concentration, high cholesterol levels, and a high pH in the bile. In contrast, pigment stones are composed of bilirubin and are more common in individuals with liver disease or hemolytic disorders.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because cholesterol stones are indeed the most common type of gallstone, accounting for approximately 80% of cases.
**Option B:** This option is incorrect because pigment stones are more common in individuals with liver disease or hemolytic disorders, not in those with a high fat diet.
**Option C:** This option is incorrect because cholesterol stones are more common in women than in men, especially after menopause.

**Clinical Pearl / High-Yield Fact**
A key risk factor for developing gallstones is a high-fat diet, particularly one that is high in saturated fats. This is because a high-fat diet can lead to an increase in cholesterol production in the liver, which can then precipitate out of solution in the gallbladder and form stones.

**Correct Answer: A. **