**Core Concept**
The process of sex differentiation from hair is based on the presence and characteristics of specific hair features, which are influenced by hormonal differences between males and females. This distinction is crucial in forensic medicine and anthropology.

**Why the Correct Answer is Right**
Sex differentiation from hair can be achieved by examining the characteristics of the hair shaft, particularly the presence of medulla, cross-sectional shape, and pigment distribution. In males, hair typically has a wider cross-sectional shape, a well-defined medulla, and a more pronounced pigment distribution, whereas in females, hair tends to be thinner, have a poorly defined or absent medulla, and a more uniform pigment distribution.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as it does not specify a valid method for sex differentiation from hair.
**Option B:** This option is incorrect as it refers to a different method of sex determination, such as analyzing genetic material or assessing secondary sex characteristics.
**Option C:** This option is incorrect as it does not accurately describe a characteristic used for sex differentiation from hair.

**Clinical Pearl / High-Yield Fact**
A classic method for sex differentiation from hair involves examining the shape of the hair shaft, with males typically exhibiting a wider cross-sectional shape.

**Correct Answer:** D.