The correct answer is A. 43 – 50 MHz.
Cordless phones use the UHF (ultra high frequency) band of the radio spectrum. This band is located between 300 MHz and 3 GHz. The UHF band is ideal for cordless phones because it has a large number of channels that can be used without interference.
The 43 – 50 MHz band is a particularly good choice for cordless phones because it is relatively free of interference from other sources, such as television and radio broadcasts. This makes it ideal for use in homes and offices where there are a lot of other electronic devices.
The other options are incorrect because they do not fall within the UHF band. Option B, 88 – 108 MHz, is the FM radio band. Option C, 540 – 1600 KHz, is the AM radio band. Option D, 200 – 540 KHz, is the longwave radio band.
These bands are not ideal for cordless phones because they are more susceptible to interference from other sources. This can cause problems with call quality and dropped calls.