Dr. Franklin has developed a new drug that makes the user feel very excited, active, and happy. It is also very addictive. Based on these drug properties, his new drug is most likely a ______ and acts on the neurotransmitter ______.
(a) Stimulant; serotonin
(b) Depressant; serotonin
(c) Stimulant; dopamine
(d) Depressant; dopamine