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

1. A
   moving along $x$ direction with frequency $10^6\text{Hz}$ and wave length $100\text{m}$.
2. B
   moving along $x$ direction with frequency $10^6\text{Hz}$ and wave length $200\text{m}$.
3. C
   moving along $-x$ direction with frequency $10^6\text{Hz}$ and wave length $200\text{m}$.
4. D
   moving along $y$ direction with frequency $2\pi \times 10^6\text{Hz}$ and wave length $200\text{m}$.