答案：B
$\left\{\begin{array}{ll}
x-y=0 & \ldots \unicode{x2460} \\
x^2+y^2+6x+ky-k =0 & \ldots \unicode{x2461}
\end{array}\right.$
$\left\{\begin{array}{ll}
x-y=0 & \ldots \unicode{x2460} \\
x^2+y^2+6x+ky-k =0 & \ldots \unicode{x2461}
\end{array}\right.$
把 $\unicode{x2460}$ 代入 $\unicode{x2461}$，可得
$\begin{array}{rcl}
x^2+x^2+6x+kx-k & = & 0 \\
2x^2+(6+k)x-k & = & 0
\end{array}$
因為該直線與圓形互不相交，所以
$\begin{array}{rcl}
\Delta & < & 0\\
(6+k)^2-4(2)(-k) & < & 0 \\
k^2+20k+36 & < & 0 \\
(k+18)(k+2) & < & 0
\end{array}$
所以，$-18 < k < -2$。
