6. As shown in Figure 2, in $\triangle A B C$, $\angle A B C=90^{\circ}$, $D$ is the midpoint of $A C$, and $B E \perp B D$ intersects the extension of $C A$ at $E$. Which of the following conclusions is correct? ( ).
(A) $\triangle B E D \backsim \triangle B C A$
(B) $\triangle B E A \backsim \triangle B C D$
(C) $\triangle A B E \backsim \triangle B C E$
(D) $\triangle B E C \backsim \triangle D B C$
6. (C).

From the problem, we have $\angle A B E=90^{\circ}-\angle A B D=\angle D B C$. Since $D$ is the midpoint of the hypotenuse $A C$ of the right triangle $\mathrm{Rt} \triangle A B C$, it follows that $\angle D B C=\angle D C B$. Therefore, $\angle A B E=\angle D B C$, so $\triangle A B E \backsim \triangle B C E$.