Final answer:
Schwann cells produce myelin sheaths in the PNS, while oligodendrocytes produce myelin sheaths in the CNS.
Step-by-step explanation:
The cells that produce myelin in the peripheral nervous system (PNS) are the Schwann cells.
In the CNS (central nervous system), a different type of glial cell called the oligodendrocyte produces myelin sheaths. The oligodendrocytes insulate the axons in the CNS.
Therefore, the correct answer is option c. Schwann cells.