Task: Text Categorization
Input (English): Question: Esters can be obtained from carboxylic acids and alcohols, by applying the Fischer esterification reaction in which: 
 Options:  <0> A base is used as a catalyst. <1> A ketone is used as the solvent. <2> A reducing reagent is used. <3> An oxidizing agent is used. <4> Acid catalysis is used.
Output (English): pharmacology