smc

Because $ABCD$ is a square, $DC=CB=16$, $DC\perp DA$, and $CB\perp BA$. Also, because $\angle DCF+\angle FCB=\angle FCB+\angle BCE=90^{\circ }$, $\angle DCF=\angle BCE$. Thus, by ASA Congruency, $△DCF\cong △BCF$. From the congruency, $CF=CE$. Using the area formula for a triangle, $CE=20$. Finally, by the Pythagorean Theorem, $BE=\sqrt{20^2-16^2}=12$, which is answer choice $\boxed{12}$.