5.设样本 ((X)_(1),(X)_(2),... ,(X)_(n+1))(ngt 1) 取自总体 sim N(mu ,(sigma )^2) , overline (X)=dfrac (1)(n)sum _(i=1)^n(X)_(i) , ^2=dfrac (1)(n-1)sum _(i=1)^n(({X)_(i)-overline (X))}^2 ,则统计量-|||-.=dfrac ({X)_(n+1)-overline (X)}(S)sqrt (dfrac {n)(n+1)} 服从 () .-|||-(A)正态分布 (B)x^2分布 (C)t分布 (D)F分布