1. The value of $\sqrt{14+6 \sqrt{5}}-\sqrt{14-6 \sqrt{5}}$ is ( ).
(A) 1
(B) $\sqrt{5}$
(C) $2 \sqrt{5}$
(D) 5
$-、 1$. (C).
$$
\begin{array}{l}
\because 14+6 \sqrt{5}=(3+\sqrt{5})^{2}, 14-6 \sqrt{5}=(3-\sqrt{5})^{2}, \\
\begin{aligned}
\therefore \text { Original expression } & =\sqrt{(3+\sqrt{5})^{2}}-\sqrt{(3-\sqrt{5})^{2}} \\
& =(3+\sqrt{5})-(3-\sqrt{5})=2 \sqrt{5} .
\end{aligned}
\end{array}
$$