If Neurotransmitters Are Linked to Depression,which of These Would Be

If neurotransmitters are linked to depression,which of these would be LEAST likely to be observed in a study?

A) lower levels of certain neurotransmitters in people who are depressed compared with those who are not depressed
B) an increase in depressive symptoms after a person take a drug that blocks the effects of certain neurotransmitters
C) a decrease in depressive symptoms once certain neurotransmitter levels in people with depression have been restored
D) a near-zero correlation between certain neurotransmitter levels and the number or severity of depressive symptoms a person reports