The graph shows a sound wave. Which statement is correct?
- AThe wave is longitudinal and has a period of $25\,\text{ms}$.
- BThe wave is longitudinal and has a frequency of $50\,\text{Hz}$.
- CThe wave is transverse and has an amplitude of $3\,\mu\text{m}$.
- DThe wave is transverse and has a wavelength of $20\,\text{ms}$.