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.
Q: Question: A selective calcium electrode is characterized by having:
Options: <0> A membrane that is a solid crystal. <1> An internal solution of 0.1 M HCl <2> An internal silver electrode. <3> A membrane of silver salts. <4> An internal aqueous solution of CaCl 2 saturated with AgCl.
A:
chemistry