A cathode-ray oscilloscope (c.r.o.) is linked to an alternating voltage. The trace shown below appears on the screen. The oscilloscope time-base setting is $0.5\,\text{ms cm}^{-1}$ and the Y-plate sensitivity is $2\,\text{V cm}^{-1}$. Which statement about the alternating voltage is correct?
- AThe amplitude is $3.5\,$cm.
- BThe frequency is $0.5\,$kHz.
- CThe period is $1\,$ms.
- DThe wavelength is $4\,$cm.