**Core Concept**
Myelination in the central nervous system (CNS) is a process that allows for faster transmission of electrical signals between neurons. This is achieved through the formation of a myelin sheath, which is composed of lipids and proteins, around the axons of neurons.

**Why the Correct Answer is Right**
The myelin forming cells in the CNS are oligodendrocytes. These cells are responsible for producing and maintaining the myelin sheath around the axons of multiple neurons. Oligodendrocytes have many extensions that wrap around the axons, forming the myelin sheath, which is rich in lipids such as myelin. This process is crucial for the proper functioning of the CNS, as it allows for the rapid transmission of electrical signals.

**Why Each Wrong Option is Incorrect**
* **Option A:** Schwann cells are responsible for myelination in the peripheral nervous system, not the CNS.
* **Option B:** Astrocytes are a type of glial cell in the CNS, but they are not responsible for myelination. Their main function is to provide support and maintenance to neurons.
* **Option D:** Microglia are the resident immune cells of the CNS, but they do not play a role in myelination.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that oligodendrocytes are responsible for myelination in the CNS, and their dysfunction can lead to demyelinating diseases such as multiple sclerosis.

**Correct Answer: C. Oligodendrocytes.**