Detailed Instructions: In this task, you are given a question and answer options for that question. Using this information, you have to classify each text into different topics: medicine, nursery, psychology, chemistry, pharmacology, biology.
Problem:Question: In ion exchange chromatography, the carboxylic acid functional group is used as: 
 Options:  <0> As a strong anion exchanger in ion exchange resins. <1> As a strong cation exchanger in ion exchange resins. <2> As a weak anion exchanger in ion exchange resins. <3> As a weak cation exchanger in ion exchange resins. <4> It is never used in ion exchange.
Solution:

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
pharmacology