A body is executing S.H.M. When its displacement from the mean position are 4 cm and 5 cm, it has velocities \[10cm\,{{s}^{-1}}\] and \[8\,cm\,{{s}^{-1}}\] respectively. Its periodic time is

• A. \[\pi /2\,s\]
• B. \[\pi s\]
• C. \[3\pi /2s\]
• D. \[2\pi s\]