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: The following may occur in multimeric form associated with the J chain: 
 Options:  <0> IgA and IgG. <1> IgD and IgM, <2> IdE and IgD. <3> IgA and IgD. <4> IgA and IgM.
[EX A]: biology

[EX Q]: Question: In suppression ion chromatography: 
 Options:  <0> A single column is used and the conductivity of the mobile phase is kept very low. <1> The eluent must be able to be removed selectively after separation and prior to the conductometric measurement. <2> The eluent incorporates a regenerating solution of strong acid flowing in the same direction as the mobile phase. <3> Weak exchangers are used from polystyrene polymers. <4> A mobile phase with ionic conductivity gradient is used.
[EX A]: chemistry

[EX Q]: Question: The determination of mercury by the cold vapor generation technique is based on the reduction of mercury in acid solution and the entrainment of the elemental mercury obtained to the absorption cell for analysis by atomic absorption. The most commonly used reducers are: 
 Options:  <0> SnCl2, for inorganic mercury and Na BH4 for both organomercury compounds and inorganic mercury. <1> Citrate, both for inorganic mercury, and organomercuriales. <2> Glutathione, especially suitable for all mercury species. <3> CaH2, for organomercurials and KMnO4 for inorganic mercury. <4> Na2SO3, for all mercury species.
[EX A]:
chemistry