6. In the Cartesian coordinate system, given four fixed points $A(-3,0), B(1,-1), C(0,3), D(-1,3)$ and a moving point $P$. Then the minimum value of $|P A|+|P B|+|P C|+|P D|$ is ( ).
(A) $4 \sqrt{2}$
(B) $3 \sqrt{2}+2 \sqrt{5}$
(C) 5
(D) $2 \sqrt{2}+3 \sqrt{5}$
6. B.

As shown in Figure 2, let $A C$ and $B D$ intersect at point $F$. Then
$$
\begin{array}{l}
|P A|+|P C| \geqslant|A C| \\
=|F A|+|F C|, \\
|P B|+|P D| \geqslant|B D| \\
=|F B|+|F D| .
\end{array}
$$

Therefore, when the moving point $P$ coincides with $F$,
$$
|P A|+|P B|+|P C|+|P D|
$$

reaches the minimum value $|A C|+|B D|=3 \sqrt{2}+2 \sqrt{5}$.