计算
$$
D=\left|\begin{array}{ccccc}
x+a_1 & a_2 & a_3 & \cdots & a_n \\
a_1 & x+a_2 & a_3 & \cdots & a_n \\
\cdots & \cdots & \cdots & \cdots & \cdots \\
a_1 & a_2 & a_3 & \cdots & x+a_n
\end{array}\right|(x \neq 0)
$$
$\text{A.}$
$\text{B.}$
$\text{C.}$
$\text{D.}$
$\text{E.}$
$\text{F.}$