设总体X~N($\mu,{\sigma}^2$),$\mu,{\sigma}^2$未知，$x_{1},x_{2},...,x_{n} $ 是来自该总体的样本，记$\overline x=\frac{1}{n}\sum\limits_{i = 1}^{n}{x_{i}}$,则对假设检验$ H_{0}:u=u_{0},H_{1}:u!=u_{0}$的拒绝域为（）

A. {${|t|>t_{\frac{\alpha}{2}}(n-1)}$}
B. {${|t|>t_{\frac{\alpha}{2}}(n)}$}
C. {${|t|>t_{\frac{\alpha}{3}}(n-1)}$}
D. {${|t|>t_{\frac{\alpha}{3}}(n)}$}