By Which Mechanism Do Selective Serotonin Reuptake Inhibitors (SSRI) Improve $\alpha$

By which mechanism do selective serotonin reuptake inhibitors (SSRI) improve depression?

A) Destroying increased amounts of serotonin
B) Making more serotonin available at the synaptic gap
C) Increasing production of acetylcholine and dopamine
D) Blocking muscarinic and $\alpha$ 1 norepinephrine receptors