Anti-depressant drugs
Anti-depressant drugs inhibit enzymes that catalyse the degradation of noradrenaline. Once the enzyme is inhibited, noradrenaline is slowly metabolised. So, it activates its receptors for longer periods of time, thereby counterbalancing the effect of depression.
Analysing the options:
Option (A):
Iproniazid is a drug that inhibits the enzymes which catalyzes the degradation of noradrenaline.
Hence, it is an anti-depressant.
Option (B):
Phenelzine is used to treat depression in people who could not be helped by other medications.
It is also an anti-depressant.
Option (C):
Equanil is used in controlling depression and hypertension.
It is also an anti-depressant.
Option (D):
Salvarsan is an antibacterial drug, used to treat syphilis. It is not an anti-depressant.
So, options (A), (B) and (C) are the correct answers.