A pendulum is hung the roof of a sufficiently high huilding and is moving freely to and fro like a simple harmonic oscillator .The acceleration of the bob of the pendulum is `20m//s^(2)` at a distance of `5m` from the meanposition .The time period of oscillation is
A. 2 s
B. `pi` s
C. `2pi` s
D. 1s