Choice A rationale: Oxytocin is the hormone responsible for the let-down reflex during breastfeeding. It is released from the posterior pituitary gland in response to the baby’s suckling. This hormone causes the milk ducts to contract and eject milk from the alveoli into the ducts, making it available for the baby.Choice B rationale: Progesterone plays a role in preparing the breast tissue for lactation during pregnancy, but it does not directly trigger the let-down reflex.Choice C rationale: Hindmilk is the milk produced later in a feeding session, which is richer in fat and calories. It is not a hormone and does not cause the let-down reflex.Choice D rationale: Foremilk is the initial milk released during breastfeeding, which is higher in water content. It is also not a hormone and does not cause the let-down reflex.