The correct option is C mammary tubules
Clusters of milk secreting cells in the mammary lobes of mammary gland are called alveoli.
The alveoli open into mammary tubules.
The mammary tubules of each lobe join to form a mammary duct.
Mammary ducts from several mammary lobes join to form an ampulla that opens into the lactiferous duct.
The lactiferous ducts open on the surface of the nipple.