Correct Answer - A::B
When displaced at an angle `theta` from its mean position, the magnitude of restoring torque is
`tau=-pE sintheta`
For small angular displacement `sintheta~~theta`
`tau=-pE theta`
The angular acceleration is `alpha=tau/I=-((pE)/I)theta=omega^2theta`
where `omega^2=(pE)/Iimplies T=(2pi)/omega=2pi sqrt(I/(pE))`