Person affected with phenylketonuria lack an enzyme that converts amino acid phenylalanine into.

The correct option is D Tyrosine

Phenylketonuria is an inherited disorder that causes an amino acid called phenylalanine to build up in the body. It is caused by a defect in the gene that helps create the enzyme needed to break down phenylalanine to tyrosine.

So, the correct answer is 'Tyrosine'.