A long thin magnet of magnetic moment $\mathrm{M}$ is bent into a semi-circle. The decrease in the magnetic moment is

• A

  $\frac{2\mathrm{M}}{\mathrm{\pi }}$
• B

  $\frac{\mathrm{\pi }\mathrm{M}}{2}$
• Correct answer
  C

  $\frac{\mathrm{M}\left(\mathrm{\pi }-2\right)}{\mathrm{\pi }}$
• D

  $\frac{\mathrm{M}\left(2-\mathrm{\pi }\right)}{2}$

Hence, the correct answer is option: 'C'.