Final answer:
a) Catechol O-methyltransferase (COMT) and monoamine oxidase (MAO) are the enzymes responsible for terminating the neurotransmitter norepinephrine.
Step-by-step explanation:
The neurotransmitter norepinephrine is terminated by the enzymes catechol O-methyltransferase (COMT) and monoamine oxidase (MAO).
Catechol O-methyltransferase (COMT) is responsible for degrading norepinephrine in the extracellular space, while monoamine oxidase (MAO) breaks down norepinephrine within the presynaptic terminal.