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
$\text{(A) always have } MH=MK\quad\\ \text{(B) always have } MH>BK\quad\\ \text{(C) sometimes have } MH=MK \text{ but not always}\quad\\ \text{(D) always have } MH>MB\quad\\ \text{(E) always have } BH<BC$
$\fbox{A}$