Which statements concerning sound and ultrasound are correct?
- Asound: humans can hear frequencies between $20\,\text{Hz}$ and $20000\,\text{Hz}$; ultrasound: the speed in air is $330\,\text{m s}^{-1}$
- Bsound: humans can hear frequencies less than $20000\,\text{Hz}$; ultrasound: the speed in air is $100\,\text{m s}^{-1}$
- Csound: the speed in air is $100\,\text{m s}^{-1}$; ultrasound: has a frequency greater than $20000\,\text{Hz}$
- Dsound: the speed in air is $330\,\text{m s}^{-1}$; ultrasound: has a frequency less than $20\,\text{Hz}$