I1.3 Given that there are $C$ integers that satisfy the equation $|x-2|+|x+1|=B$, find the value of $C$
$$
|x-2|+|x+1|=3
$$

If $x<-1,2-x-x-1=3 \Rightarrow x=-1$ (rejected)
If $-1 \leq x \leq 2,2-x+x+1=3 \Rightarrow 3=3$, always true $\therefore-1 \leq x \leq 2$
If $2<x, x-2+x+1=3 \Rightarrow x=2$ (reject)
$\therefore-1 \leq x \leq 2$ only
$\because x$ is an integer, $\therefore x=-1,0,1,2 ; C=4$