14.单选题-|||-设 sim N((M)_(2)(O)^2) ,则下列叙述中错误的是 ()-|||-(A) dfrac (X-mu )({sigma )^2}sim N(0,1)-|||-B . Xin (a,b) =phi (dfrac (b-mu )(sigma ))-Phi (dfrac (a-mu )(sigma ))-|||-C) (x)=Phi (dfrac (x-mu )(sigma )) .-|||-) |x-mu |leqslant k0 =2Phi (k)-1(kgt 0)