To understand the correct sequence in the route of milk ejection from the human mammary gland, we need to follow the anatomical pathway that milk travels. Let's break down each part and its function in the sequence:

Mammary alveolus (C): These are the milk-producing structures in the mammary gland. Milk is initially produced here and stored in the alveolar cells.

Mammary tubule (E): The mammary alveoli are connected to small ductules called mammary tubules, which transport the milk out of the alveoli.

Mammary duct (A): The mammary tubules merge to form larger ducts known as mammary ducts. These ducts conduct the milk toward the nipple area.

Ampulla (D): The mammary ducts widen into lactiferous sinuses, known as ampullae, which act as reservoirs for the milk before it is ejected.

Lactiferous duct (B): Finally, the milk travels through the lactiferous ducts, which open at the nipple for milk ejection.

So, the correct sequence is:

$$\mathrm{C} \rightarrow \mathrm{E} \rightarrow \mathrm{A} \rightarrow \mathrm{D} \rightarrow \mathrm{B}$$

Thus, the correct answer is:

Option C