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

[EX Q]: Which human body system is a complex network of nervous tissue that carries electrical messages throughout the body?
[EX A]: the nervous system

[EX Q]: What works by providing a lower energy pathway from reactants to products?
[EX A]: catalyst

[EX Q]: A black solid by itself, this element is incredibly important because of what it makes when it combines with many other elements, including oxygen?
[EX A]:
carbon