How much of the hair's total weight comes from the cortex?

The cortex is the middle layer of the hair shaft and is responsible for giving hair its strength and elasticity. It also contains the pigment that gives hair its color. While the outer cuticle layer also contributes to the weight of the hair, it is thinner and less dense than the cortex. Therefore, it is safe to assume that the majority of the hair's total weight comes from the cortex, making option C, 90%, the most accurate answer choice. Option A, 50%, and option B, 75%, are too low and do not take into account the contribution of the other layers. Option D, 100%, is incorrect as it suggests that the cuticle does not contribute to the weight of the hair at all, which is false.