A.0.9772B.0.5C.0.1587D.0.02275
A.5B.10C.0.5D.20
A.Var(a)=0(a是常量)B.Var(aX)=a2Var(X)(a是常量)C.Var(XY)=Var(X)Var(Y)D.Var(X+Y)=Var(X)+Var(Y)(X和Y彼此獨(dú)立)