The correct option is A Electric energy density is equal to the magnetic energy density
Electric energy density is equal to the magnetic energy density.
Here, UE=12ϵoE2.....(1)
and UB=B22μo.....(2)
Moreover, E=cB and c=1√μoϵo
In equation 1,
UE=12ϵo(cB)2UE=12ϵo(1√μoϵoB)2UE=B22μo=UB
Hence, option C is correct.