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已知集合,若,则等于 ( )
A.1 B.2 C.1或2.5 D. 1或2
已知集合,,若,则等于( )
A.1 B.1或2 C.1或 D.2
已知集合,,若,则等于
A.1 B.2 C.1或 D.1或2