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.

Question: Under physiological conditions, the secondary structure of the most frequent DNA in the cells is: 
 Options:  <0> B-DNA. <1> Z-DNA. <2> A-DNA. <3> G-DNA. <4> H-DNA.
biology

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.
nursery

Question: In gas chromatography, derivatization is very common, with several objectives. One of those discussed below is not among them: 
 Options:  <0> Increase the volatility of non-volatile compounds. <1> Avoid the decomposition of a compound, improving its stability. <2> Reduce the absorption on active surfaces of the walls of the column and the solid support. <3> Fragment the analyte in molecular ions of easier separation. <4> Improve the separation of closely related compounds with a very poor separation.

chemistry