2.84 Let the real number $x$ satisfy $|2-x|=2+|x|$, then $\sqrt{(x-1)^{2}}$ equals
(A) $x-1$.
(B) $1-x$.
(C) $\pm(x-1)$.
(D) 1 .
(Shanghai Junior High School Mathematics Competition, 1986)
[Solution] Given $|2-x|=2+|x|$, we know $x \leqslant 0$. $\therefore x-1<0$. Then $\sqrt{(x-1)^{2}}=1-x$. Therefore, the correct choice is $(B)$.