AHSME 1970 Problem 20

Lines $HK$ and $BC$ lie in a plane. $M$ is the midpoint of the line segment $BC$, and $BH$ and $CK$ are perpendicular to $HK$. Then we $\text{(A) always have } MH=MK \\ \text{(B) always have } MH>BK \\ \text{(C) sometimes have } MH=MK \text{ but not always} \\ \text{(D) always have } MH>MB \\ \text{(E) always have } BH<BC$