How Are Levels of the Neurotransmitters Norepinephrine and Serotonin Related

How are levels of the neurotransmitters norepinephrine and serotonin related to depression?

A) People with unusually high or unusually low levels of neurotransmitters are more likely to be depressed.
B) People with high levels of norepinephrine and low levels of serotonin are more likely to be depressed.
C) People with higher levels of these neurotransmitters are more likely to be depressed.
D) People with lower levels of these neurotransmitters are more likely to be depressed.