单项选择题
A.P(A+B)=P(A) B.P(AB)=P(A) C.P(B|A)=P(B) D.P(B-A)=P(B)-P(A)
A、ρ={R1(WY),R2(XZ)} B、ρ={R1(WZ),R2(XY)} C、ρ={R1(WXY),R2(XZ)} D、ρ={R1(WX),R2(YZ)}