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 $g[f(x)]=$
A. $\begin{cases}2+x^2, & x < 0 \\ 2-x, & x \geq 0\end{cases}$
B. $\begin{cases}2-x^2, & x < 0 \\ 2+x, & x \geq 0\end{cases}$
C. $\begin{cases}2-x^2, & x < 0 \\ 2-x, & x \geq 0\end{cases}$
D. $\begin{cases}2+x^2, & x < 0 \\ 2+x, & x \geq 0\end{cases}$