Definition: In this task, you are given a multiple-choice question about healthcare. Answer the question based on your information and classify your answers into '1', '2', '3', and '4'.
Input: Question: What does the amperometric detector measure in high performance liquid chromatography (HPLC)? 
 Options:  <1> Potential difference. <2> Electric conductivity. <3> Thermal conductivity. <4> Electric resistance. <5> Intensity of electric current.
