Task: Text Categorization
Input (English): Question: Allopurinol, as an inhibitor of xanthine oxidase: 
 Options:  <0> It is suicidal, reversible. <1> It is suicidal, irreversible. <2> It is analogous to the transition state, reversible. <3> Inhibits the enzyme by proteolysis. <4> Allopurinol does not inhibit that enzyme.
Output (English): chemistry