Answer:
A nerve impulse
Explanation:
It's important to note that these signals not only connect the brain and spinal cord, but they also send signals to muscles and glands. People talk about nerve impulses when they talk about the electrical signal that goes down an axon.
The answer is tree hope this helped :)
The answer is b it is being bred for a trait that is favored by humans
B) One swims freely and the other often lives attached to a hard surface.
