**Core Concept**
Carbohydrates are an essential energy source for the human body. They are stored in various forms to be utilized as needed. The primary storage form of carbohydrates in humans is a complex polysaccharide that serves as a readily mobilizable energy reserve.

**Why the Correct Answer is Right**
Carbohydrates are stored in the liver and muscles as glycogen, a highly branched polymer of glucose molecules. This storage form allows for rapid mobilization of glucose into the bloodstream when energy demands increase. Glycogen is synthesized from glucose via the enzyme glycogen synthase, and it is broken down into glucose by glycogen phosphorylase. The resulting glucose is then released into the bloodstream or utilized by nearby cells for energy production.

**Why Each Wrong Option is Incorrect**
**Option A:** This is not a correct storage form of carbohydrates in humans.
**Option B:** Lipids are a separate class of biomolecules, not a storage form of carbohydrates.
**Option C:** Proteins are not a storage form of carbohydrates, although they can be broken down to release glucose through gluconeogenesis.

**Clinical Pearl / High-Yield Fact**
Glycogen storage diseases, such as glycogen storage disease type I (GSD I), result from deficiencies in enzymes involved in glycogen metabolism. These diseases can lead to severe hypoglycemia and other metabolic disturbances.

**Correct Answer: C. Glycogen**