Adrenaline Is the Only Known Neurotransmitter in Humans

Adrenaline is the only known neurotransmitter in humans.

A) True. It triggers all appropriate body responses as directed by the brain.
B) False. There are at least 25 neurotransmitters that do different things but work together to produce body responses.
C) True. It is responsible for the "fight or flight" response in all animals, not just humans.
D) False. There are at least 25, and they all produce different responses but only one response at a time.
E) True. This is the only known one but scientists suspect that there are more they haven't found yet.