A simple pendulum is executing S.H.M. around point $\mathrm{O}$ between the end points $B$ and $C$ with a periodic time of $6 \mathrm{~s}$. If the distance between $\mathrm{B}$ and $\mathrm{C}$ is $20 \mathrm{~cm}$ then in what time will the bob move from $C$ to $D$ ? Point $D$ is at the mid-point of $C$ and $\mathrm{O}$.
(A) $1 \mathrm{~s}$
(B) $2 \mathrm{~s}$
(C) $3 \mathrm{~s}$
(D) $4 \mathrm{~s}$