What are the smallest units of meaning in a language?

Ted runs from the biology laboratory straight to his therapist's office. He is sweating and fear is etched on his face

He asks the therapist to apologize to his teacher and says he hopes she will understand that his arachnophobia made it difficult for him to _____. a) speak in class b) dissect a cat c) look at a spider d) take a blood sample

What two chemical compounds are known to be particularly important neurotransmitters in the brain?

a. Glutamate and acetylcholine b. Gamma-aminobutyric acid and dopamine c. Norepinephrine and serotonin d. Serotonin and dopamine