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.
Input: Question: The alkaline error that occurs in glass electrodes for the average pH:
Options: <0> It is due to the presence of an excessive concentration of protons that is replaced by sodium ions in the glass membrane. <1> Occurs at neutral pH due to the absence of protons. <2> It takes place at very alkaline pH, in which the sodium ion behaves as if it were a proton. <3> It appears as a consequence of the dehydration of the glass membrane. <4> It occurs when the electrode is introduced into pure water due to the dissolution of the sodium ions in the membrane.
Output:
chemistry