设总体 sim N((3.4)^2) ,(X1,X2,···X16)为来自总体X的简单随机样本,X为样-|||-本均值,则 () .-|||-A. (overline (X)-3)sim N(0,1) ;-|||-B. dfrac (1)(4)(overline (X)-3)sim N(0,1) ;-|||-C. (overline (X)-3)sim N(0,1) ;-|||-D. dfrac (1)(4)overline (X)-3sim N(0,1) ;