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若集合,,若,则等于( )
A.1 B.2 C. D.1或2
已知集合,,若,则等于( )
A.1 B.1或2 C.1或 D.2
集合P={x|x2=1},Q={x|mx=1},若QP,则m等于 ( )
A.1 B.-1 C.1或-1 D.0,1或-1