**Core Concept**
Glycogen is a complex carbohydrate stored in the liver and muscles, serving as a readily available energy source. During starvation, glycogen stores are depleted to maintain blood glucose levels.

**Why the Correct Answer is Right**
During starvation, the body initially relies on glycogen stored in the liver and muscles for energy. The glycogen is broken down into glucose-1-phosphate by glycogen phosphorylase, which is then converted to glucose-6-phosphate by phosphoglucomutase. Glucose-6-phosphate is then released into the bloodstream to maintain blood glucose levels. The liver's glycogen stores are depleted within 12-24 hours of starvation, after which the body begins to break down fat and protein for energy.

**Why Each Wrong Option is Incorrect**
**Option A:** There is no clear evidence to suggest that glycogen stores are depleted within 6 hours of starvation.
**Option B:** While glycogen stores are depleted during starvation, the exact timeframe is not 48 hours.
**Option C:** Glycogen stores are depleted within 12-24 hours of starvation, not 72 hours.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the liver's glycogen stores are depleted relatively quickly during starvation, after which the body begins to break down fat and protein for energy. This process is crucial for understanding the metabolic adaptations that occur during prolonged fasting or starvation.

**Correct Answer: C. 12-24 hours**