The correct option is D Oxytocin
The neural signal for parturition is initiated by the fully developed fetus and placenta as mild uterine contraction called foetal ejection reflex. Foetal ejection reflex stimulates the pituitary to release oxytocin, which results in stronger contractions. Contractions result in more secretion of oxytocin and further contractions which together result in expulsion of the baby or parturition.