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: The term isocratic is used in high pressure liquid chromatography (HPLC) when: 
 Options:  <1> The mobile phase is at a constant temperature. <2> The stationary phase is in equilibrium with the mobile phase. <3> The mobile phase consists of a single solvent with a constant composition. <4> The flow rate of the mobile phase is regulated. <5> All the options are correct.
