The magnetic moment of a current carrying loop is $2.1\times {10}^{-25}{\mathrm{Am}}^2$.  The magnetic field at a point on its axis at a distance of $1\stackrel{\mathrm{o}}{\mathrm{A}}$ is

• A

  $4.2\times {10}^{-2}\mathrm{Wb}/{\mathrm{m}}^2$

• B

  $4.2\times {10}^{-3}\mathrm{Wb}/{\mathrm{m}}^2$

• C

  $4.2\times {10}^{-4}\mathrm{Wb}/{\mathrm{m}}^2$

• D

  $4.2\times {10}^{-5}\mathrm{Wb}/{\mathrm{m}}^2$