Final answer:
The secretion of sebum is stimulated by hormones.
Step-by-step explanation:
The sebaceous glands are simple alveolar glands that secrete a substance known as sebum. The secretion of sebum is stimulated by hormones. Hormones play a crucial role in regulating various physiological processes in the body, including the production of sebum by the sebaceous glands. These hormones become active during puberty and contribute to the increase in sebum production, which is why teenagers often experience oily skin.