Two particles $A$ and $B$ have equal charges but different masses $M_{A}$ and $M_{B}$. After being accelerated through the same potential difference,they enter a region of uniform magnetic field and describe paths of radii $R_{A}$ and $R_{B}$ respectively. Then $M_{A} : M_{B}$ is

• A
  $\frac{R_{A}}{R_{B}}$
• B
  $\frac{R_{B}}{R_{A}}$
• C
  $\left(\frac{R_{A}}{R_{B}}\right)^{2}$
• D
  $\left(\frac{R_{B}}{R_{A}}\right)^{2}$