$A$ charged particle moving along a straight line path enters a uniform magnetic field of $4 \ mT$ at right angles to the direction of the magnetic field. If the specific charge of the charged particle is $8 \times 10^7 \ C \ kg^{-1}$,the angular velocity of the particle in the magnetic field is

• A
  $64 \times 10^4 \ rad \ s^{-1}$
• B
  $32 \times 10^4 \ rad \ s^{-1}$
• C
  $16 \times 10^4 \ rad \ s^{-1}$
• D
  $48 \times 10^4 \ rad \ s^{-1}$