In Understanding the Problems with Attempts at Human Racial Classification

In understanding the problems with attempts at human racial classification, why is it important to understand the difference between genotype and phenotype?

A) Phenotypic traits typically used to classify humans into races go together as genetic units.
B) Phenotypic similarities and differences always have a genetic basis.
C) Attempts at human racial classification have typically used genotypic traits like blood type as markers of common ancestry, and these traits pass on from generation to generation in discrete bundles.
D) Although phenotypic characteristics may change, the genetic material of populations stays the same for a long time.
E) Attempts at human racial classification have typically used phenotypic traits like skin color as markers of common ancestry, but many such traits do not reflect shared genetic material. Instead, they are often the result of different populations biologically adapting to similar environmental stressors in similar ways.