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 method of continuous variations is used in molecular absorption spectrophotometry to: 
 Options:  <1> Determine the position of the isobestic point in a mixture of absorbent species. <2> Calculate the exact position of the absorption maximum of an absorbent complex. <3> Obtain the pH corresponding to the end point of the titration of an absorbing acid or base. <4> Calculate the stoichiometry of an absorbent complex. <5> Calculate the exact value of the dissociation constant of an absorbent acid.
