**Core Concept**
Glycoproteins are a class of proteins that contain carbohydrate molecules (glycans) covalently attached to their polypeptide side-chains. This attachment is known as glycosylation, and it plays a crucial role in the structure, function, and stability of glycoproteins.

**Why the Correct Answer is Right**
Glycoproteins contain a type of carbohydrate called oligosaccharides, which are short chains of sugars (polysaccharides) that are bonded to the protein backbone. These oligosaccharides can be either N-linked (attached to the nitrogen atom of asparagine or arginine) or O-linked (attached to the oxygen atom of serine, threonine, or hydroxylysine). Oligosaccharides in glycoproteins are composed of various monosaccharides, such as glucose, galactose, N-acetylglucosamine, and N-acetylgalactosamine, which are linked together through glycosidic bonds.

**Why Each Wrong Option is Incorrect**
**Option A:** Monosaccharides are single sugar molecules (e.g., glucose, fructose) and are not the correct form of carbohydrate present in glycoproteins.
**Option B:** Polysaccharides are long chains of sugar molecules (e.g., starch, cellulose) and are not typically found in glycoproteins.
**Option C:** Disaccharides are two sugar molecules bonded together (e.g., sucrose, lactose) and are not the correct form of carbohydrate present in glycoproteins.

**Clinical Pearl / High-Yield Fact**
Glycosylation is a critical post-translational modification that affects the function, stability, and cellular trafficking of glycoproteins. Abnormal glycosylation patterns are associated with various diseases, including cancer, neurodegenerative disorders, and infectious diseases.

**Correct Answer:** C.