Half life biological of oxytocin:: (A) 2-3 min, (B) 3-4 min, (C) 5-6 min, (D) 7-8 min
Answer is B. Oxytocin

It is a nonapeptide (Peptide of nine amino acids).
Released by posterior pituitary and synthesized in the supra optic and paraventricular nucleus of hypothalamus.
Half life 3–4 minutes.
Duration of action – 20 minutes.
Mechanism of action – Acts through calcium mediated channels to initiate myometrial contractions.