Two blocks, each of mas s m are connected by a massless spring of spring constant fr and the system is placed on a friction less surface as shown. Time period of system for small oscillations will be:
 

• A

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

• B

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

• C

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

• D

  $2\mathrm{\pi }\sqrt{\frac{\mathrm{m}}{4\mathrm{k}}}$