A sine wave of wavelengh $\lambda$ is travelling in a medium. The minimum distance between the two particles, always having same speed, is

• A

  $\frac{\mathrm{\lambda }}{4}$

• B

  $\frac{\mathrm{\lambda }}{3}$

• C

  $\frac{\mathrm{\lambda }}{2}$

• D

  $\lambda$