8. Given a function $f(x)$ defined on $\mathbf{R}$, which is increasing on $(-\infty, 2)$, and the graph of $f(x+2)$ is symmetric about the $y$-axis. Then ( ).
(A) $f(-1)f(3)$
(C) $f(-1)=f(3)$
(D) $f(0)=f(3)$
8. A.

From the problem, we know that $f(x)$ is symmetric about $x=2$.
Also, the function $f(x)$ is monotonically increasing on $(-\infty, 2)$, hence
$$
\begin{array}{l}
f(-1)=f(5)<f(3), \\
f(0)=f(4)<f(3) .
\end{array}
$$