Question

what are the small gaps in the myelin sheath called?
oligodendrocytes
nodes of ranvier
synaptic clefts
axon hillocks
schwann cells

Explanation:

The myelin sheath is interrupted at regular intervals by small gaps. These gaps are known as the Nodes of Ranvier. Oligodendrocytes are cells that form myelin in the central nervous - system. Synaptic clefts are the spaces between neurons at synapses. Axon hillocks are the part of a neuron where the axon originates. Schwann cells form myelin in the peripheral nervous system.

Answer:

B. Nodes of Ranvier