The correct option is
B Milk ejection
Oxytocin is a peptide hormone secreted from posterior lobe of pituitary gland i.e. neurohypophysis. It causes uterine contractions during childbirth. It is secreted after dilation of cervix during parturition. It also stimulates ejection of milk in mammary glands in response to suckling stimulus.
So, the correct answer is 'Milk ejection'.