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: A rat pathogen that has fleas as vectors of transmission to humans is: 
 Options:  <0> Rickettsia rickettsii. <1> Yersinia pestis <2> Borrelia burgdorferi. <3> Ehrlichia ewingii. <4> Brucella abortus.
[EX A]: biology

[EX Q]: Question: In the synthesis of DNA, the quinolones act: 
 Options:  <0> Joining the double helix and thus blocking the progress of the replication fork. <1> Interlacing in the double helix and thus causing errors in the transcription. <2> On DNA gyrase. <3> As nucleotide analogs that are incorporated into DNA. <4> About DNA polymerases.
[EX A]: biology

[EX Q]: Question: The chemosmotic theory: 
 Options:  <0> It was proposed by Singer and Nicholson. <1> Explains the mechanism of phosphorylation at the substrate level. <2> It requires that the membranes in which it forms are closed compartments. <3> It does not explain the synthesis of ATP in photosynthesis. <4> It has nothing to do with redox reactions.
[EX A]:
biology