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: Osmium oxide (VIII), OsO4: 
 Options:  <0> It is a compound in a state of oxidation very common among transition metals. <1> It is the only binary compound of osmium with oxygen. <2> It has the structure of rhenium trioxide. <3> It is inert compared to alkaline hydroxides. <4> It is used as an oxidant in organic chemistry.
[EX A]: chemistry

[EX Q]: Question: The reaction of 1H-indole with electrophiles takes place selectively on the atom in position: 
 Options:  <0> one. <1> two. <2> 3. <3> Four. <4> 5.
[EX A]: chemistry

[EX Q]: Question: Beta-adrenergic receptor blocking drugs: 
 Options:  <0> They cause hypotension in individuals with normal blood pressure. <1> They increase the atrio-ventricular conduction velocity. <2> They cause negative inotropism. <3> They provoke a positive chronotropic effect. <4> They increase the secretion of renin.
[EX A]:
pharmacology