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A.1 B.-1 C.-1或1 D.2
设集合,则等于
A.{1,2,3,4} B.{1,2,4,5} C.{1,2,5} D.{3}
A.{1,2,3,4} B.{1,2,4,5}
C. {1,2,5} D.{3}