The electric field part of an electromagnetic wave in a medium is represented by $E_x = 0$; $E_y = 2.5 \frac{N}{C} \cos \left[ (2\pi \times 10^6 \frac{rad}{s})t - (\pi \times 10^{-2} \frac{rad}{m})x \right]$; $E_z = 0$. The wave is:

• A
  Moving along $-x$ direction with frequency $10^6 \, Hz$ and wavelength $200 \, m$.
• B
  Moving along $y$ direction with frequency $2\pi \times 10^6 \, Hz$ and wavelength $200 \, m$.
• C
  Moving along $x$ direction with frequency $10^6 \, Hz$ and wavelength $100 \, m$.
• D
  Moving along $x$ direction with frequency $10^6 \, Hz$ and wavelength $200 \, m$.