Of the following individuals, the one MOST likely to commit suicide would be a:

A) 10-year-old with high serotonin activity.
B) 10-year-old with low serotonin activity.
C) 40-year-old with high serotonin activity.
D) 40-year-old with low serotonin activity.

Answer: D) 40-year-old with low serotonin activity.