Q.The hormone controlling parturition is

Parturition is triggered by oxytocin, which causes vigorous uterine contractions — the answer is (c).

Parturition is the act of childbirth (expulsion of the mature foetus). It is induced by a neuroendocrine reflex:

• Signals from the fully developed foetus and placenta trigger release of oxytocin from the mother's posterior pituitary.
• Oxytocin causes powerful contractions of the uterine (myometrial) smooth muscle; these contractions stimulate more oxytocin release (a positive feedback loop), building up until the baby is delivered. …