Definition: In this task, you are given a multiple-choice question about healthcare. Answer the question based on your information and classify your answers into '1', '2', '3', and '4'.
Input: Question: The Chichibabin reaction is an example of nucleophilic substitution in a ring of: 
 Options:  <1> Benzene. <2> Anthracene <3> Biphenyl <4> Pyridine <5> Pirrol.
