The potential energy of a $1 \mathrm{~kg}$ particle free to move along the $x$ -axis is given by:
$$
V(x)=\left(\frac{x^{4}}{4}-\frac{x^{2}}{2}\right) \mathrm{J}
$$
The total mechanical energy of the particle is $2 \mathrm{~J}$ Then, the maximum speed (in $\mathrm{m} / \mathrm{s}$ ) is:
(a) 2
(b) $\frac{3}{\sqrt{2}}$
(d) $\frac{1}{\sqrt{2}}$
(c) $\sqrt{2}$