A proton, a deuteron and an alpha particle are accelerated through potentials of $V,\: 2V\: and\: 4V$ respectively. Their velocities will bear a ratio

Question

$\begin {array} {1 1} (a)\;1:1:1 & \quad (b)\;1: \sqrt 2 : 1 \\ (c)\;\sqrt 2 : 1 : 1 & \quad (d)\;1 : 1: \sqrt 2 \end {array}$