Why is milk produced only after delivery, not before?ALevels of luteinizing hormone and follicle-stimulating hormone are too low during pregnancy to supportmilk productionBHigh levels of progesterone during pregnancy suppress milk productionCThe alveolar cells of the breast do not reach maturity until after deliveryDHigh levels of oxytocin are required for milk production to begin, and oxytocin is not secreted until the baby stimulates the nipple