Task: Text Categorization
Input (English): Question: The reaction of Diels Alder is an example of reaction: 
 Options:  <0> Concerted and stereospecific. <1> Nucleophilic substitution of order 2. <2> Nucleophilic substitution of order 1. <3> Condensation polymerization. <4> Nucleophilic addition.
Output (English): pharmacology