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圆C1:x2+y2-2x-6y+9=0关于直线x-y-1=0对称的曲线方程为 ( )
A.x2+y2+2x+6y+9=0 B.x2+y2-6x-2y+9=0
C.x2+y2-8x+15=0 D.x2+y2-8x-15=0