_____ Triggers the "Let-Down Reflex" Where the Mammary Glands Are

_____ triggers the "let-down reflex" where the mammary glands are triggered to eject milk into the milk ducts.

A)  Oxytocin 
B)  Estrogen 
C)  Prepartum amenorrhea 
D)  Postpartum amenorrhea 
E)  FSH