Final answer:
Sebaceous glands secrete "oil" into hair follicles. They produce sebum that lubricates and waterproofs the skin and hair, and has antibacterial properties.
Step-by-step explanation:
The glands that secrete "oil" into a hair follicle are sebaceous glands. These glands produce an oily substance called sebum, which is secreted into hair follicles and helps lubricate and waterproof the skin and hair. Sebum also has antibacterial properties and prevents water loss from the skin. Most sebaceous glands are associated with hair follicles, and they are found all over the body except for the palms of the hands and soles of the feet.