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: The cells of the stomach that are responsible for the secretion of hydrochloric acid are:
Options: <0> The main cells. <1> The G cells <2> The parietal cells. <3> The enterocytes. <4> The mucosites of surface.
[A]: nursery

[Q]: Question: Esters can be obtained from carboxylic acids and alcohols, by applying the Fischer esterification reaction in which:
Options: <0> A base is used as a catalyst. <1> A ketone is used as the solvent. <2> A reducing reagent is used. <3> An oxidizing agent is used. <4> Acid catalysis is used.
[A]: pharmacology

[Q]: Question: Transcription factors:
Options: <0> They bind to chromatin by interaction with histone H2A. <1> They bind to RNA and regulate the start of transcription. <2> They join the DNA. <3> They are organized into nucleosomes. <4> They regulate DNA methylation.
[A]:
pharmacology