The electric field part of an electromagnetic wave in a medium is represented by 

${\mathrm{E}}_{\mathrm{x}}=0,$ ${\mathrm{E}}_{\mathrm{y}}=2.5\mathrm{N}/\mathrm{C}\cos [(2\mathrm{\pi }\times {10}^6\mathrm{rad}/\mathrm{s})\mathrm{t}-(\mathrm{\pi }\times {10}^{-2}\mathrm{rad}/\mathrm{m})\mathrm{x}]$   And ${\mathrm{E}}_{\mathrm{z}}=0$. Then the wave is

Moving along x direction with frequency ${10}^6 \mathrm{Hz}$ and wavelength 200 m

Moving along y direction with a frequency $2\mathrm{\pi }\times {10}^6 \mathrm{Hz}$ and wavelength 200 m.

Moving along x direction with frequency ${10}^6 \mathrm{Hz}$ and wavelength 100 m

Moving along –x direction with frequency ${10}^6 \mathrm{Hz}$ and wavelength 200 m