A pendulum is hung from the roof of a sufficiently high building and is moving freely to and fro like a simple harmonic oscillator. The acceleration of the bob of the pendulum is $20 \; m/s^2$ at a distance of 5 m from the mean position. The time period of oscillation is :

Question

( A ) $\pi$ s
( B ) 2 s
( C ) 1 s
( D ) 2 $\pi$ s