Given a scientific question, generate a correct answer to it.

[EX Q]: What is the outer layer of an axon that acts like a layer of insulation, similar to the plastic that encases an electrical cord?
[EX A]: myelin sheath

[EX Q]: Organic compounds are molecules built around what element?
[EX A]: carbon

[EX Q]: What type of plants have vascular tissue but do not have seeds?
[EX A]:
seedless vascular plants