One end of a spring of force constant k is fixed to a vertical wall and the other to a block of mass m resting on a smooth horizontal surface. There is another wall at a distance \[{{x}_{0}}\] from the black. The spring is then compressed by \[2{{x}_{0}}\] and released. The time taken to strike the wall is

• A. \[\frac{1}{6}\pi \sqrt{\frac{k}{m}}\] 
• B. \[\sqrt{\frac{k}{m}}\]
• C.   Zero
• D. \[\frac{\pi }{4}\sqrt{\frac{k}{m}}\]