A bat travels straight towards a stationary ultrasound detector at a speed of $25.0\,\text{m s}^{-1}$ while producing ultrasound pulses with frequency $40.0\,\text{kHz}$. The speed of sound in air is $330\,\text{m s}^{-1}$. What frequency is registered by the ultrasound detector?
- A$37.0\,\text{kHz}$
- B$37.2\,\text{kHz}$
- C$43.0\,\text{kHz}$
- D$43.3\,\text{kHz}$