In this task, you are given a question and answer options for that question. Using this information, you have to classify each text into different topics: medicine, nursery, psychology, chemistry, pharmacology, biology.

[EX Q]: Question: Immunoglobulin isotype change affects: 
 Options:  <0> The constant regions of the heavy chains. <1> The constant regions of the light chains. <2> The totality of heavy chains. <3> The entire immunoglobulin molecule. <4> The hypervariable regions of the heavy chains.
[EX A]: biology

[EX Q]: Question: Indicate which of the following is an alteration of the pyrimidine metabolism: 
 Options:  <0> Thrombophilia <1> Phenylketonuria <2> Wilson's disease <3> Urine disease with the smell of maple syrup. <4> Orotic hereditary acidity.
[EX A]: pharmacology

[EX Q]: 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.
[EX A]:
chemistry