1. In the real domain, the value of the expression
||$\sqrt{-(x-4)^{2}}-1|-2|$ is ( ).
(A) can only be 3
(B) can only be 1
(C) can only be 2
(D) none of the above answers is correct
$-1 .(\dot{B})$
$$
\begin{array}{l}
\because-(x-4)^{2} \leqslant 0, \text { and }-(x-4)^{2} \geqslant 0, \\
\therefore(x-4)^{2}=0 . \\
\therefore \text { original expression }=|| 0-1|-2|=|1-2|=|-1|=1 .
\end{array}
$$