Task: Text Categorization
Input (English): Question: The cause of phenylketonuria is a hereditary deficit of: 
 Options:  <0> Homogentisate dioxygenase. <1> Tyrosine aminotransferase. <2> Phenylalanine hydroxylase. <3> Dihydropteridine oxidase. <4> Tryptophan dioxygenase.
Output (English): biology