Two travelling waves ${\mathrm{y}}_1 = \mathrm{A} \sin \left[\mathrm{k}\right(\mathrm{x}-\mathrm{ct}\left)\right] \mathrm{and} {\mathrm{y}}_2 = \mathrm{A} \sin \left[\mathrm{k}\right(\mathrm{x}+\mathrm{ct}\left)\right]$ are superimposed on string. The distance between adjacent nodes is

• A

  $\frac{\mathrm{ct}}{\mathrm{\pi }}$

• B

  $\frac{\mathrm{ct}}{2\mathrm{\pi }}$

• C

  $\frac{\mathrm{\pi }}{2\mathrm{k}}$

• D

  $\frac{\mathrm{\pi }}{\mathrm{k}}$