How Is the Milk Produced by the Mammary Glands Propelled

How is the milk produced by the mammary glands propelled toward the nipple?

A) by the contraction of myoepithelial cells surrounding the alveoli
B) by segmentation of the myometrium of mammary glands
C) by the contraction of milk-secreting glands called the alveoli
D) by the peristaltic movement of mammary glands
E) by mass movement in response to external stimuli