Task: Text Categorization
Input (English): Question: Of the following reaction mechanisms, in which there is an inversion of the configuration from the reactant to the product of the reaction ?: 
 Options:  <0> Bimolecular nucleophilic substitution (SN2). <1> Unimolecular elimination (E1). <2> Unimolecular nucleophilic substitution (SN1). <3> Addition Markovnikov. <4> Addition anti-Markovnikov.
Output (English): chemistry