6. As shown in the figure, in isosceles $\triangle ABC$, $CD$ is the altitude on the base $AB$, $E$ is the midpoint of the leg $BC$, and $AE$ intersects $CD$ at $F$. Now, three routes are given:
(a) A $\rightarrow F \rightarrow C \rightarrow E \rightarrow B \rightarrow D \rightarrow A$;
(b) $A \rightarrow C \rightarrow E \rightarrow B \rightarrow D \rightarrow F \rightarrow A$;
(c) $A \rightarrow D \rightarrow B \rightarrow E \rightarrow F \rightarrow C \rightarrow A$. Let their respective lengths be $L(a)$, $L(b)$, $L(c)$.
Then, among the following three inequalities:
$L$ (a) $<L$ (b), $L$ (a) $<L$ (c),
$L$ (b) $<L$ (c)

the number of those that must be true is:
(A) 0;
(B) 1;
(d) 2;
(D) 3.
Ans: $[B]$. 

 

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