**Core Concept**
The cell wall of Gram-positive bacteria is a critical structure that provides rigidity and maintains the bacterial shape. It is composed of a thick layer of peptidoglycan, also known as murein, which is responsible for the osmotic stability of the cell.

**Why the Correct Answer is Right**
The peptidoglycan layer in Gram-positive bacteria is composed of a glycan backbone linked by peptide chains. This layer is cross-linked by penicillin-binding proteins (PBPs), which are essential for cell wall synthesis and repair. The peptidoglycan layer is also rich in teichoic acids, which are linked to the glycan backbone and play a role in cell wall stability and signaling. The thick peptidoglycan layer in Gram-positive bacteria is responsible for their characteristic Gram-positive staining pattern.

**Why Each Wrong Option is Incorrect**
* **Option A:** Lipopolysaccharides are found in the outer membrane of Gram-negative bacteria, not Gram-positive bacteria.
* **Option B:** Glycoproteins are found in the cell membrane of many eukaryotic cells, but are not a characteristic component of the Gram-positive bacterial cell wall.
* **Option C:** Lipoteichoic acids are a type of teichoic acid found in Gram-positive bacteria, but they are not the primary component of the cell wall.

**Clinical Pearl / High-Yield Fact**
The thickness of the peptidoglycan layer in Gram-positive bacteria is a key factor in their resistance to beta-lactam antibiotics, such as penicillin and ampicillin. These antibiotics work by inhibiting cell wall synthesis and causing the cell to lyse.

**Correct Answer:** C. Peptidoglycan.