Which part of the hair holds the tint on eyebrows and eyelashes?

The cortex is the correct choice because it is the part of the hair that contains the pigment, allowing for color to be held and maintained. In the case of eyebrows and eyelashes, the cortex plays a crucial role in the absorption of tint during the coloring process. This layer is made up of long keratin fibers that provide strength and structure, and it is where the natural color resides.

The other parts mentioned serve different functions. The medulla, while present in some types of hair, is not significant in finer hair like that of eyebrows and eyelashes. The cuticle is the outer protective layer that can influence the overall appearance and health of the hair but does not hold pigment. Lastly, the follicle is the part of the skin that produces hair but does not hold color itself. Understanding the role of the cortex in hair coloration is vital for those practicing beauty treatments, as it directly affects the effectiveness of tinting processes.