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.

[EX Q]: Question: About free radicals: 
 Options:  <0> They are compounds that contain two or three unpaired electrons in an outer orbital. <1> Reactive oxygen species (ROS) in the cell are only generated enzymatically. <2> Hydrogen peroxide is the most damaging radical in the cell. <3> The hydroxyl radical originates non-enzymatically (Heber-Weiss reaction) and damages proteins and DNA. <4> Oxygen is a triradical.
[EX A]: chemistry

[EX Q]: Question: A cyclic voltammetry: 
 Options:  <0> It is based on a stationary broadcasting regime. <1> It uses macroelectrodes as working electrodes. <2> He never needs a potentiostatic system. <3> It is always done in a non-agitated solution. <4> It uses a square wave potential format as an excitation system.
[EX A]: chemistry

[EX Q]: Question: The hepatitis B virus: 
 Options:  <0> It has circular double-stranded RNA as a genetic material. <1> It has circular single-stranded RNA as a genetic material. <2> It is transmitted by air. <3> Encode a reverse transcriptase. <4> It does not have tissue tropism.
[EX A]:
biology