The correct answer is option C, i.e., Plasma membrane.

Explanation:
Glycocalyx is a layer of carbohydrates that covers the plasma membrane of most cells. It is composed of glycolipids and glycoproteins that protrude from the plasma membrane's surface. The glycocalyx plays a crucial role in various cellular processes, including cell adhesion, cell-to-cell communication, and cellular recognition.

Functions of Glycocalyx:
The glycocalyx performs the following functions in the cell:

1. Cell-to-cell recognition: The glycocalyx acts as a marker for cell recognition, allowing cells to identify each other, which is necessary for cell communication, cell adhesion, and immune responses.

2. Protection: Glycocalyx provides a protective barrier for the cell membrane and helps to prevent the cell from being damaged by external factors such as bacteria, viruses, and other harmful substances.

3. Lubrication: The glycocalyx provides a lubricating layer that makes it easier for cells to move and slide past each other.

4. Cell adhesion: Glycocalyx helps cells to adhere to each other, which is essential for the formation of tissues and organs.

5. Cell signaling: Glycocalyx plays a critical role in cell signaling, allowing cells to communicate with each other and respond to different signals.

Conclusion:
In conclusion, the glycocalyx is associated with the plasma membrane of most cells. It is a layer of carbohydrates that plays a crucial role in various cellular processes, including cell-to-cell communication, cell adhesion, and cellular recognition.