Task: Question Answering
Input (English): Question: What is the purpose of the phthalyl group in phthalisulfatiazole ?: 
 Options:  <1> Improve intestinal absorption. <2> Prevent intestinal absorption. <3> Improve the passage through the blood-brain barrier. <4> Prevent passage through the blood-brain barrier. <5> Increase the affinity towards the therapeutic target of the drug.
Output (English): 2