$\because F=-\frac{d U}{d x} \Rightarrow F=-8 \sin 2 x$
For small oscillations, $x$ will be small hence
$F=-8(2 x)=-16 x \quad \Rightarrow k=16$ and $m=1 \mathrm{kg}$
$\therefore \omega^{2}=\frac{\mathrm{k}}{\mathrm{m}}=\frac{16}{1}=16 \Rightarrow \omega=4$
$\Rightarrow \mathrm{T}=\frac{2 \pi}{\omega}=\frac{2 \pi}{4}=\frac{\pi}{2}$
$(a)$ Potential energy is always equal to its $K.E.$
$(b)$ Average potential and kinetic energy over any given time interval are always equal.
$(c)$ Sum of the kinetic and potential energy at any point of time is constant.
$(d)$ Average $K.E.$ in one time period is equal to average potential energy in one time period.
Choose the most appropriate option from the options given below: