6. As shown in Figure 1, in $\triangle A B C$, $\angle A>\angle B>$ $\angle C, I$ is the incenter. Three routes are given:
(1) $I \rightarrow A \rightarrow C \rightarrow B \rightarrow I$;
(2) $I \rightarrow C \rightarrow B \rightarrow A \rightarrow I$;
(3) $I \rightarrow B \rightarrow A \rightarrow C \rightarrow I$.
If the lengths of these routes are denoted as $l_{1} 、 l_{2} 、 l_{3}$, respectively, then the shortest one is ( ).
(A) $l_{1}$
(B) $l_{2}$
(C) $l_{3}$
(D) Cannot be determined
6.C.

Since $\angle A > \angle B > \angle C$, then $a > b > c$.
Let $A I = x, B I = y, C I = z$ (it is easy to know $xI D$,
$$

i.e., $x + (a - b) > y$.
Therefore, $b + y < a + x$.
Similarly, $c + z < b + y$.
Thus, $c + z < b + y < a + x$.
From this, comparing $l_{1}, l_{2}, l_{3}$, we can see that $l_{3}$ is the shortest.