Which of the following situations would place a child at risk to inherit PKU from his or her parents?

A) The father is heterozygous (normal and mutant PAH alleles); the mother is homozygous normal.
B) The mother is heterozygous (normal and mutant PAH alleles); the father is homozygous normal.
C) Both parents are heterozygous (normal and mutant PAH alleles) for the PAH gene.
D) The father is homozygous for the mutant PAH alleles; the mother is homozygous normal.
E) The mother is homozygous for the mutant PAH alleles; the father is homozygous normal.