Which, If Any, of the Following Is Incorrect? When Used

Multiple Choice

Which, if any, of the following is incorrect? When used in human genetics, the term allele

A) describes any individual gene variant.
B) refers to a nuclear gene at a locus on a single chromosome
C) primarily means an individual DNA sequence copy at a locus that is common to two homologous chromosomes.
D) is often used loosely at the protein level to describe a protein made by a single copy of a nuclear gene.