Final answer:
The glia that speeds up electrical signals by myelinating axons in the central nervous system are called oligodendrocytes, whereas Schwann cells perform this function in the peripheral nervous system. The answer is option E.
Step-by-step explanation:
The glia that are present throughout the vertebrate brain or spinal cord and surround axons to speed up electrical signals are called oligodendrocytes and Schwann cells. Oligodendrocytes form myelin sheaths around axons in the central nervous system (CNS), such as the brain and spinal cord, with one oligodendrocyte potentially providing myelin for multiple axons. Conversely, Schwann cells produce the myelin sheath around axons in the peripheral nervous system (PNS) where each Schwann cell myelinates only one segment of an axon.
The correct answer to the student's question is e. oligodendrocytes, as these are the specific glia mentioned in the context of the CNS. Even though Schwann cells also myelinate axons, they are functionally located in the PNS rather than the CNS.