A conducting circular loop is placed in a uniform magnetic field, B = 0.025 T with its plane perpendicular to the loop. The radius of the loop is made to shrink at a constant rate of 1 mm/s. The induced emf when the radius is 2 cm, is :

• A

  2 μV

• B

  2$\mathrm{\pi }$ μV

• C

  $\mathrm{\pi }$ μV

• D

  $\frac{\mathrm{\pi }}{2}\mathrm{\mu V}$