**Core Concept**
A homopolysaccharide is a type of polysaccharide composed of a single type of sugar molecule. This contrasts with heteropolysaccharides, which contain multiple types of sugar molecules. Homopolysaccharides can serve as energy storage molecules, structural components of cell walls, or as signaling molecules.

**Why the Correct Answer is Right**
The correct answer is a type of homopolysaccharide, specifically glycogen. Glycogen is a complex carbohydrate stored in the liver and muscles, comprising a long chain of glucose molecules. It serves as an energy storage molecule, broken down into glucose during periods of low energy and converted back into glycogen when energy is abundant.

**Why Each Wrong Option is Incorrect**
**Option A:** This is not a type of homopolysaccharide. Chitin is a heteropolysaccharide composed of N-acetylglucosamine units.
**Option B:** This is not a type of homopolysaccharide. Cellulose is a heteropolysaccharide composed of glucose units, but it contains a specific arrangement of beta-1,4 glycosidic bonds that distinguish it from other glucose-based polysaccharides like glycogen.
**Option D:** This is not a type of homopolysaccharide. Starch is a heteropolysaccharide composed of glucose units, but it contains a mixture of alpha-1,4 and alpha-1,6 glycosidic bonds.

**Clinical Pearl / High-Yield Fact**
Glycogen storage diseases (GSDs) are a group of disorders caused by defects in enzymes involved in glycogen synthesis or breakdown. GSDs can result in severe hypoglycemia, lactic acidosis, and liver enlargement.

**Correct Answer:** C. Glycogen