A proton and a deuteron are both accelerated through the same potential difference and enter in a magnetic field perpendicular to the direction of the field. If the deuteron follows a path of radius $$R$$, assuming the neutron and proton masses are nearly equal, the radius of the proton's path will be

A

$$\sqrt{2}R$$

B

$$\frac{R}{\sqrt{2}}$$

C

$$\frac{R}{2}$$

D

$$R$$