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.

Q: Question: The 2,4-diaminopteridine systems, such as aminopterin or methotrexate, are good antitumor agents since they reduce the biosynthesis of purines and pyrimidines by inhibiting the enzyme: 
 Options:  <0> Timidylate synthetase <1> Aromatase <2> Topoisomerase <3> Reverse transcriptase <4> Dihydrofolate reductase.

A: pharmacology
****
Q: Question: Inhibits the integrase of HIV the: 
 Options:  <0> Efavirenz. <1> Tenofovir <2> Ritonavir <3> Emtricitabine. <4> Raltegravir

A: biology
****
Q: Question: The placenta is a derivative of: 
 Options:  <0> The zona pellucida. <1> The trophoblast. <2> The ectoderm <3> The mesoderm <4> The primitive line.

A:
medicine
****