6. As shown in Figure 1, points $E$, $F$, $G$, $H$, $M$, $N$ are on the sides $BC$, $AC$, $AB$ of $\triangle ABC$, respectively, and $NH \parallel MG \parallel BC$, $ME \parallel NF \parallel AC$, $GF \parallel EH \parallel AB$. There are two ants, one black and one white, starting from point $F$ at the same time and speed. The black ant crawls along the path $F \rightarrow N \rightarrow H \rightarrow E \rightarrow M \rightarrow G \rightarrow F$, and the white ant crawls along the path $F \rightarrow B \rightarrow A \rightarrow C \rightarrow F$. Therefore, ( ).
(A) the black ant returns to point $F$ first
(B) the white ant returns to point $F$ first
(C) both ants return to point $F$ at the same time
(D) which ant returns to point $F$ first depends on the positions of the points
6.C.

In Figure 1, quadrilaterals $C F N H$, $A H E M$, and $B M G F$ are all parallelograms. Therefore, the distance crawled by the black ant is
$$
\begin{array}{l}
F N+N H+H E+E M+M G+G F \\
=C H+C F+A M+A H+B F+B M \\
=(C H+A H)+(C F+B F)+(A M+B M) . \\
=A C+B C+A B=\text { the distance crawled by the white ant. }
\end{array}
$$