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

[Q]: The nervous system is characterized by electrical signals that are sent from one area to another. whether those areas are close or very far apart, the signal must travel along this?
[A]: axon

[Q]: What two basic types of feather does a bird have?
[A]: flight and down

[Q]: What kind of rock's makeup is changed by heat and or pressure?
[A]:
metamorphic