**Core Concept**
Starch is a type of complex carbohydrate, also known as a polysaccharide, composed of glucose units linked by glycosidic bonds. It serves as a primary source of energy storage in plants and is a common dietary component in many foods.

**Why the Correct Answer is Right**
Starch is a polysaccharide consisting of amylose and amylopectin, which are two types of glycogen-like molecules. Amylose is a linear chain of glucose units, while amylopectin is a branched chain of glucose units. The glycosidic bonds linking these glucose units are formed through condensation reactions, where water molecules are eliminated. The structure of starch allows it to be easily broken down into glucose units during digestion, releasing energy for the body to use.

**Why Each Wrong Option is Incorrect**
**Option A:**
This option is incorrect because starch is not a type of protein; it is a complex carbohydrate.

**Option B:**
This option is incorrect because cellulose is a type of polysaccharide, but it is composed of glucose units linked by β-glycosidic bonds, making it indigestible by humans.

**Option C:**
This option is incorrect because glycogen is a complex carbohydrate, but it is composed of glucose units linked by α-glycosidic bonds and is primarily stored in animal tissues, not plants.

**Clinical Pearl / High-Yield Fact**
When considering the structure and function of starch, it is essential to remember that the ratio of amylose to amylopectin can affect the digestibility and glycemic index of starch-containing foods.

**Correct Answer:** C. Glycogen.