Final answer:
Oligodendrocytes are a type of glial cell found in the CNS that insulate axons with a myelin sheath, with one oligodendrocyte myelinating multiple axon segments. Option D is correct.
Step-by-step explanation:
Oligodendrocytes are a type of glial cell found in the central nervous system (CNS) that play a crucial role in insulating axons with a myelin sheath. Unlike Schwann cells that myelinate only one axon segment in the peripheral nervous system (PNS), an oligodendrocyte can extend its processes to insulate multiple axon segments within the CNS.
This allows for efficient electrical signal transmission along the neurons. The myelinated axons facilitate faster and more efficient electrochemical nerve impulses which are crucial for the proper functioning of the nervous system. Therefore, the correct answer to the student's question is D) Glial cell.