Definition: 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.
Input: Question: What is the purpose of the phthalyl group in phthalisulfatiazole ?: 
 Options:  <0> Improve intestinal absorption. <1> Prevent intestinal absorption. <2> Improve the passage through the blood-brain barrier. <3> Prevent passage through the blood-brain barrier. <4> Increase the affinity towards the therapeutic target of the drug.
Output:
pharmacology