The equation of the stationary wave is $\mathrm{y}=2\mathrm{Asin}\left(\frac{2\mathrm{\pi ct}}{\mathrm{\lambda }}\right)\cos \left(\frac{2\mathrm{\pi x}}{\mathrm{\lambda }}\right)$ Which of the following statements is wrong? 

• A

  The unit of ct is same as that of $\mathrm{\lambda }$. 

• B

  The unit of x is same as that of $\mathrm{\lambda }$. 

• C

  The unit of $2\mathrm{\pi c}/\mathrm{\lambda }$ is same as that of $2\mathrm{\pi x}/\mathrm{\lambda t}$. 

• D

  The unit of $\mathrm{c}/\mathrm{\lambda }$ is same as that of $\mathrm{x}/\mathrm{\lambda }$.