This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Nervous system, Subject name: Physiology
Myelin sheath in CNS is produced by 
Select and explain. 
A. Oligodendrocyte, B. Schwann cell, C. Microglia, D. Macroglia
A: Oligodendrocyte
Answer: A: Oligodendrocyte 
Explanation: Oligodendrocytes and Schwann cells are involved in myelin formation around axons in the CNS and peripheral nervous system respectively. Ref: Ganong&;s review of medical physiology; 23rd edition; pg: 80.