If a simple harmonic motion is represented by $\frac{d^2x}{dt^2} + \propto x = 0$, its time peroid is :

Question

( A ) $2 \pi \propto$
( B ) $\frac{2 \pi}{\propto}$
( C ) $\frac{2 \pi}{\sqrt{\propto}}$
( D ) $2 \pi \sqrt{\propto}$