$A$ cyclotron's oscillator frequency is $n$ and the radius of the dees is $r$. The operating magnetic field $(B)$ for accelerating protons of charge $q$ and the kinetic energy of the protons produced by the accelerator are respectively ($m$ and $v$ are the mass and velocity of the proton).

• A
  $\frac{2 \pi n m}{q}, \frac{q v B r}{2}$
• B
  $\frac{\pi n m}{q}, \frac{q v B r}{2}$
• C
  $\frac{2 \pi n m}{q}, q v B r$
• D
  $\frac{4 \pi n m}{q}, \frac{q v B r}{2}$