Cperiodic but not a simple harmonic
c
(c)
Given, potential energy curve closely represents potential energy of a simple harmonic oscillator $\left(U=\frac{1}{2} k x^2\right.$, shown in dotted line $)$
In region $r_1 < x < r_2$, the potential energy is less than total energy, so motion of particle in this region is oscillatory.
Also, the potential energy curve is not symmetric about $x=r_{\text {. }}$.
$\therefore$ Motion is not a simple harmonic.
