记行列式 $\left|\begin{array}{cccc}x-2 & x-1 & x-2 & x-3 \\ 2 x-2 & 2 x-1 & 2 x-2 & 2 x-3 \\ 3 x-3 & 3 x-2 & 4 x-5 & 3 x-5 \\ 4 x & 4 x-3 & 5 x-7 & 4 x-3\end{array}\right|$ 为 $f(x)$, 则方程 $f(x)=0$ 的的个数为
$\text{A.}$ 1.
$\text{B.}$ 2 .
$\text{C.}$ 3 .
$\text{D.}$ 4 .