Which system includes skin, oil, and sweat glands?

The integumentary system is the correct answer because it encompasses the skin and its appendages, which include oil glands (sebaceous glands) and sweat glands (sudoriferous glands). This system serves several vital functions, including protecting the body from environmental hazards, regulating body temperature through sweat production, and providing a barrier against pathogens. Additionally, the skin plays a key role in sensation and the synthesis of vitamin D.

In contrast, the endocrine system is involved in hormone production and regulation but does not include skin or its glands. The nervous system is responsible for transmitting signals throughout the body but does not encompass the skin or related structures. The muscular system is focused on movement and locomotion, consisting of muscle tissues, but does not include the skin or glandular components. Therefore, the integumentary system is distinct in that it specifically includes skin and its associated glands, making it the comprehensive answer to the question.