Definition: In this task, you are given a multiple-choice question about healthcare. Answer the question based on your information and classify your answers into '1', '2', '3', and '4'.
Input: Question: The cause of phenylketonuria is a hereditary deficit of: 
 Options:  <1> Homogentisate dioxygenase. <2> Tyrosine aminotransferase. <3> Phenylalanine hydroxylase. <4> Dihydropteridine oxidase. <5> Tryptophan dioxygenase.
