Studies of chromosomal and mitochondrial DNA suggest that every locus exhibits some variability in its nucleotide sequence. Which of the following does NOT apply in those studies?

A) Every locus exhibits some variability in its nucleotide sequence among individuals from a single population.
B) Every locus exhibits some variability in its nucleotide sequence between populations of the same species.
C) Every locus exhibits some variability in its nucleotide sequence between related species.
D) Every locus exhibits some variability in its nucleotide sequence within an individual.