Which of the following statements is true?

a. the dopamine hypotheis of schizophrenia believes that schizophrenic individuals have really high levels of dopamine
b. the dopamine hypotheis of schizophrenia believes that schizophrenic individuals have excess activity at the dopamine synapses
c. the glutamate hypothesis of schizophrenia states that people with schizophrenia have low levels of glutamate
d.'the glutamate hypothesis of schizophrenia states that people with schizophrenia have low levels of glutamate activity