问题
以下哪个选项是一个行向量或者说行矩阵？选项
[A]. $\begin{bmatrix} a_{1} & & \\ & a_{2} & \\ & & a_{3} \end{bmatrix}$[B]. $\left(a_{1}, a_{2}, \cdots, a_{n}\right)$
[C]. $\left(\begin{array}{c} 1 \\ 1 \\ \vdots \\ 1 \end{array}\right)$
[D]. $\left(\begin{array}{c} b_{1} \\ b_{2} \\ \vdots \\ b_{m} \end{array}\right)$
$\left(a_{1}, a_{2}, \cdots, a_{n}\right)$