Is there a SPARQL way to...

Hi,

1)
  is it possible to write  a SPARQL query that given this data


ex:1 a ex:A
ex:2 a ex:A
ex:2 a ex:B
ex:3 a ex:A
ex:3 a ex:C
ex:4 a ex:B
ex:4 a ex:C

  returns only all subjects which belong only to class A?
  So in my example, only "ex:1" should  be returned.
  Ah,  and  resources can have more than two classes.

2)  Is  there  any  kind  of collection on the web of common SPARQL problems and
queries that solve it? Maybe some wiki page?

Kind Regards,
Max
--
       Max Völkel
   www.Xam.de
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