Final answer:
The mammary glands, which produce and secrete milk, are composed of clusters of alveoli and duct systems, classifying them as compound alveolar glands. The correct answer to the student's question is D) compound alveolar.
Step-by-step explanation:
Mammary glands are specialized structures responsible for milk production and secretion in mammals. These glands are considered to be modified sweat glands and are composed of lactiferous ducts, lactiferous sinuses, lobules, and clusters of alveoli. Each alveolus is a milk-secreting structure lined with lactocytes, or cuboidal cells.
During lactation, milk is produced in these alveoli and transported through the duct system to be eventually secreted out of the nipple. Consequently, because the mammary glands are made of these clusters of alveoli and duct systems, they are best described as compound alveolar glands. Therefore, the answer to the student's question is D) compound alveolar.