Two identical particles each of mass $m$ are separated by a distance $d$. The axis of rotation passes through the midpoint of $d$ and is perpendicular to the length $d$. If $K$ is the rotational kinetic energy of the system,then the angular frequency $\omega$ is:

• A
  $2d \sqrt{\frac{m}{K}}$
• B
  $\frac{d}{2} \sqrt{\frac{K}{m}}$
• C
  $\frac{2}{d} \sqrt{\frac{K}{m}}$
• D
  $\frac{d}{4} \sqrt{\frac{m}{K}}$