8. If the equation in terms of $x$
$$
|x+1|+|x-1|=a
$$

has real roots, then the range of values for the real number $a$ is (. ).
(A) $a \geqslant 0$
(B) $a>0$
(C) $a \geqslant 1$
(D) $a \geqslant 2$
8. D.
$$
\begin{array}{l}
|x+1|+|x-1| \\
=\left\{\begin{array}{cc}
2 x & x \geqslant 1 ; \\
2, & -1<x<1, \\
-2 x & x \leqslant-1 .
\end{array}\right.
\end{array}
$$

Therefore, $a \geqslant 2$.