(c)
$\frac{\left( v_{av} \right)_{1}}{\left( v_{av} \right)_{2}} = \sqrt{\frac{T_{1}}{T_{2}}}$
Given, $T_{1} = 150 + 273 = 423\ K$
$T_{2} = 50 + 273 = 323\ K$
$\therefore\ \frac{\left( v_{av} \right)_{1}}{\left( v_{av} \right)_{2}} = \sqrt{\frac{T_{1}}{T_{2}}} = \sqrt{\frac{423}{323}} = \frac{1.14}{1}$