The parts of the integumentary system that share a common function are sebum and sweat. Both sebum (produced by sebaceous glands) and sweat (produced by sweat glands) play crucial roles in regulating body temperature and maintaining skin hydration and integrity.
The other options—scales and follicles, hair and horns, feathers and fur—represent different types of protective or insulating structures but do not serve the same specific physiological functions as sebum and sweat.