The magnitude of displacement of a particle moving in a circle of radius a with constant angular speed $\mathrm{\omega }$ varies with time t is

• A

  2a $\sin \mathrm{\omega t}$

• B

  2a $\sin \frac{\mathrm{\omega t}}{2}$

• C

  2a $\cos \mathrm{\omega t}$

• D

  2a $\cos \frac{\mathrm{\omega t}}{2}$