1.67 If $x<0$, then $x-\sqrt{(x-1)^{2}}$ equals
(A) 1.
(B) $1-2 x$.
(C) $-2 x-1$.
(D) $1+2 x$.
(E) $2 x-1$.
(29th American High School Mathematics Examination, 1978)
[Solution]
$$
\begin{array}{c}
\left|x-\sqrt{(x-1)^{2}}\right|=|x-| x-1||=|x-(1-x)| \\
=|-1+2 x|=1-2 x .
\end{array}
$$

Therefore, the correct choice is $(B)$.