4. The number of real solutions to the equation $\left|x^{2}-3 x+2\right|+\left|x^{2}+2 x-3\right|=11$ is ( ).
(A) 0
(B) 1
(C) 2
(D) 4
4. C.

The original equation is $|x-1|(|x-2|+|x+3|)=11$.
By discussing four cases: $x \leqslant -3$, $-3 < x \leqslant 2$, $2 < x \leqslant 1$, and $x > 1$, we know that there are 2 real solutions that satisfy the equation.