ln the following arrangement the system is initially at rest. The 5 kg block is now released. Assuming the pulleys and string to be massless and smooth, the acceleration of block 'C' will be

• A

  zero

• B

  2.5 $\mathrm{m}/{\mathrm{s}}^2$

• C

  $\frac{10}{7} \mathrm{m}/{\mathrm{s}}^2$

• D

  $\frac{5}{7}\mathrm{m}/{\mathrm{s}}^2$