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抛物线的焦点坐标为
A.(0,–1) B.(0,1) C.(0,) D.(0,)
抛物线的焦点坐标为 ( )
A.(0,1) B.(1,0) C.(2,0) D.(0,2)
抛物线的焦点坐标为( )
A.(0,) B. (0,) C.(,0) D.(,0)