The diagram shows the display of an electromagnetic wave on a cathode-ray oscilloscope. The time base setting is $0.20\ \mu\text{s cm}^{-1}$. Which statement is correct?
- AThe frequency of the wave is $2.5\ \text{MHz}$ and it lies in the radio wave region of the electromagnetic spectrum.
- BThe frequency of the wave is $2.5\ \text{MHz}$ and it lies in the microwave region of the electromagnetic spectrum.
- CThe frequency of the wave is $5.0\ \text{MHz}$ and it lies in the radio wave region of the electromagnetic spectrum.
- DThe frequency of the wave is $5.0\ \text{MHz}$ and it lies in the microwave region of the electromagnetic spectrum.