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: Controls the passage of substances to the central nervous system: 
 Options:  <0> Meninges. <1> Choroid plexus. <2> Hemato-encephalic barrier. <3> White substance <4> Schwann cells and oligodendrocytes.

A: biology
****
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.

A: chemistry
****
Q: Question: Generates blunt DNA fragments the restriction enzyme: 
 Options:  <0> Bam HI. <1> Hae III. <2> Hind III. <3> Eco RI. <4> Eco RII.

A:
biology
****