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))`