A progressive wave has a frequency of $1.5\,\text{kHz}$ and moves through a medium with a speed of $340\,\text{m s}^{-1}$. What is the smallest distance between two points on the wave that are separated by a phase difference of $70^{\circ}$?
- A$4.4\,\text{cm}$
- B$8.8\,\text{cm}$
- C$18\,\text{cm}$
- D$23\,\text{cm}$