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,

A) the terms dominant and recessive apply equally to alleles and phenotypes.
B) dominant describes a phenotype that is manifested in the heterozygote, that is, the phenotype is attributable to just a single allele.
C) recessive describes a phenotype that is manifest as a result of the combined effects of both alleles at a locus.
D) the AB blood group is an example of a co-dominant phenotype.