Final answer:
Sebaceous glands produce sebum, an oily substance with antibacterial properties that inhibits bacterial growth, waterproofs skin and hair, and prevents them from drying out. The correct answer is C)
Step-by-step explanation:
The type of gland that secretes an acidic oily substance that inhibits bacterial growth is the sebaceous gland. These glands produce sebum, which is an oily substance containing lipids and other compounds that have antibacterial properties. Sebum is secreted into hair follicles and helps to waterproof and prevent the skin and hair from drying out. Furthermore, the fatty acids contained in sebum also help to inhibit the growth of microorganisms on the skin surface. Therefore, the correct answer is C) sebaceous glands.