Abnormal levels of may lead to schizophrenia and parkinson’s disease.
a. gaba (gamma-aminobutyric acid)
b. glutamate
c. serotonin
d. dopamine

The answer is D. Dopamine.

Explanation:

Dopamine is a neurotransmitter produced at the level of the central nervous system (CNS). It is a hormone synthesized by the brain that allows the connection between neurons, very important for the neuro-muscular function of the organism. In the case of parkinson, there is a destruction of the cells that are responsible for the production of dopamine in the majority and this leads to the lack of control of the voluntary movements; while in ezquisophrenia it is due to an excess of dopamine.