The correct option is A Inheritance of a condition like phenylketonuria as an autosomal recessive trait
The above-given pedigree chart shows an autosomal recessive disorder. In this pedigree chart, the trait is not expressed by both parents. If the parents are carriers of abnormal genes, then their offspring can express the trait. Therefore, the above pedigree chart shows the inheritance of a condition like phenylketonuria as an autosomal recessive trait.
So, option (a) is the correct answer.