Task: Question Answering
Input (English): Question: In ion exchange chromatography, the carboxylic acid functional group is used as: 
 Options:  <1> As a strong anion exchanger in ion exchange resins. <2> As a strong cation exchanger in ion exchange resins. <3> As a weak anion exchanger in ion exchange resins. <4> As a weak cation exchanger in ion exchange resins. <5> It is never used in ion exchange.
Output (English): 4