Which is the duct in mammary gland through which milk is sucked out?

Lactiferous duct.

The correct answer is Option (4) – Lactiferous duct.

Mammary lobes containing clusters of cells called alveoli. The cells of alveoli secrete milk, which is stored in the cavities (lumens) of alveoli. The alveoli open into mammary tubules. The tubules of each lobe join to form a mammary duct. Several mammary ducts join to form a wider mammary ampulla which is connected to lactiferous duct through which milk is sucked out.