The diagram displays the trace on an oscilloscope screen. The initial peak is produced when a sound pulse is sent out. The later, smaller peak is the echo that returns from a wall. The trace sweeps across the screen in $24\,\text{ms}$. How long does it take the sound to reach the wall?
- A$4.5\,\text{ms}$
- B$9.0\,\text{ms}$
- C$12\,\text{ms}$
- D$32\,\text{ms}$