We use the equation
$\begin{align*}E^2 = m^2 c^4 + p^2 c^2\end{align*}$
Plugging in the given values of $E$ and $m$ , we find that
$\begin{align*}\left(1.5 \mbox{ MeV}\right)^2 = \left(0.5 \;\mathrm{MeV}\mathrm{/}\mathrm{c}^2\right)^2 c^4 + p^2 c^2 \Rightar...$
$\sqrt{2}$ evaluates to $1.414$ , therefore answer (C) is correct.

Solution to 1992 Problem 85