# S1: In an electromagnetic wave, the average energy density of electric field is equal to the average energy density of the magnetic field  S2: Electric and magnetic fields are related as $E = cB$
$\begin {array} {1 1} (a)\;\text{S1 and S2 are true; S2 is a correct explanation of S1.}\\ (b)\;\text{S1 and S2 are true; S2 is not a correct explanation of S1.} \\ (c)\;\text{S1 is true; S2 is false} \\ (d)\;\text{S1 is false; S2 is true.} \end {array}$