设 $g(x)=\left\{\begin{array}{ll}2-x & x \leq 0 \\ x+2 & x>0\end{array}, f(x)=\left\{\begin{array}{ll}x^2 & x < 0 \\ -x & x \geq 0\end{array}\right.\right.$ ，则 $g[f(x)]=$
$\text{A.}$ $\begin{cases}2+x^2, & x < 0 \\ 2-x, & x \geq 0\end{cases}$
$\text{B.}$ $\begin{cases}2-x^2, & x < 0 \\ 2+x, & x \geq 0\end{cases}$
$\text{C.}$ $\begin{cases}2-x^2, & x < 0 \\ 2-x, & x \geq 0\end{cases}$
$\text{D.}$ $\begin{cases}2+x^2, & x < 0 \\ 2+x, & x \geq 0\end{cases}$