A transverse progressive wave with wavelength $\lambda$ is produced on a stretched string. The graph illustrates how displacement $y$ varies with distance $x$ at one specific instant. The wave has displacement $+y_1$ when $x = \dfrac{\lambda}{8}$. What are the next two values of $x$ at which the displacement $y$ is once more equal to $+y_1$?
- A$\dfrac{3\lambda}{8}$ and $\dfrac{5\lambda}{8}$
- B$\dfrac{3\lambda}{8}$ and $\dfrac{9\lambda}{8}$
- C$\dfrac{5\lambda}{8}$ and $\dfrac{9\lambda}{8}$
- D$\dfrac{9\lambda}{8}$ and $\dfrac{17\lambda}{8}$