What was the investigation? But from my best guess I'm assuming it's the second option. This may be incorrect.
Answer:
D
Explanation:D Sorry if I'm wrong!
Rather, each myelin sheath insulates the axon over a single long section and, in general, each axon comprises multiple long myelinated sections separated from each other by short myelin sheath-gaps called nodes of Ranvier. ... In the CNS, axons carry electrical signals from one nerve cell body to another.
4. Gene Pool is not a mechanism, thus your answer!
