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: A selective calcium electrode is characterized by having: 
 Options:  <1> A membrane that is a solid crystal. <2> An internal solution of 0.1 M HCl <3> An internal silver electrode. <4> A membrane of silver salts. <5> An internal aqueous solution of CaCl 2 saturated with AgCl.
