An object that is oscillating creates waves on the surface of a liquid. The object carries out $20$ vibrations each second. The distance between adjacent crests is $3.0\,\text{cm}$. What is the speed of the waves?
- A$0.15\,\text{cm s}^{-1}$
- B$6.7\,\text{cm s}^{-1}$
- C$60\,\text{cm s}^{-1}$
- D$120\,\text{cm s}^{-1}$