Correct option is C
For a plane electromagnetic wave traveling in vacuum along the z-direction:
• The electric field vector (E) is perpendicular to the direction of wave propagation (z-axis), say along x-axis.
• The magnetic field vector (B or H) is also perpendicular to the direction of propagation but lies along the y-axis.
• Thus, E ⊥ B ⊥ direction of propagation.