(c) Maximum velocity $V_{\max} = a\omega$
$\omega = \frac{2\pi}{T}\ \therefore V_{\max} = \frac{2\pi a}{T},\ i.e.,\ V \propto \frac{a}{T}$
$\therefore\frac{V_{1}}{V_{2}} = \frac{a_{1}}{a_{2}} \times \frac{T_{2}}{T_{1}} = \frac{1}{2} \times \frac{1}{3} = \frac{1}{6}$
$\therefore V_{2} = 6V_{1} = 6V$