A plane electromagnetic wave propagating along y – direction can have the following pair of electric field  $\left(\overrightarrow{E}\right)$ and magnetic field  $\left(\overrightarrow{B}\right)$ components.

EM wave is propagating in y-direction. $\overrightarrow{E}$  and  $\overrightarrow{B}$ vectors are perpendicular to direction of propagation of wave. Hence neither of them have a component along y-axis. Both vectors have to be in x-z plane. $E_x,B_{z}or{E}_z,B_x$  is the correct answer