$F =-\frac{ dU }{ dx }=-4(+\sin 4 x ) 4=-16 \sin (4 x )$
For small $\theta$
$\sin \theta \approx \theta$
$F=-64\,x$
$a=-64\,x / m=-16\,x$
$\omega^{2}=16$
$T =\frac{2 \pi}{\omega}=\frac{\pi}{2}$


Statement $I :$ A second's pendulum has a time period of $1$ second.
Statement $II :$ It takes precisely one second to move between the two extreme positions.
In the light of the above statements, choose the correct answer from the options given below: