Two blocks each of mass m are connected with springs each of force constant fr as shown in the Fig. Initially the springs are relaxed. The mass A is displaced to the left and ^B to the right by the same amount and released, then the time period of oscillation is:
 

• A

  $2\mathrm{\pi }\sqrt{\frac{\mathrm{m}}{\mathrm{k}}}$

• B

  $2\mathrm{\pi }\sqrt{\frac{\mathrm{m}}{2\mathrm{k}}}$

• C

  $\mathrm{\pi }\sqrt{\frac{\mathrm{m}}{\mathrm{k}}}$

• D

  $\mathrm{\pi }\sqrt{\frac{\mathrm{m}}{2\mathrm{k}}}$