Task: Question Answering
Input (English): Question: The arenio ion is a reaction intermediate that is formed in the reactions of: 
 Options:  <1> Electrophilic addition. <2> Electrophilic aromatic substitution. <3> Nucleophilic substitution. <4> Nucleophilic addition. <5> Aromatic nucleophilic substitution.
Output (English): 2