In an electromagnetic wave, the average energy density associated with magnetic field is

• A

  ${{\mathrm{Li}}^2}_0/2$

• B

  ${\mathrm{B}}^2/2{\mathrm{\mu }}_0$

• C

  ${\mathrm{\mu }}_0{\mathrm{B}}^2/2$

• D

  ${\mathrm{\mu }}_0/2{\mathrm{B}}^2$