Answer: option A= 500 Hz.
Step-by-step explanation:
The full meaning of CW is continuous waveform or continuous wave. Continuous waveform during wireless telegraph radio transmission is also known as undamped waves. Around 1920, damped wave spark transmitters were replaced by continuous wave vacuum tube transmitters. Continuous waveform is some wave of constant amplitude and frequency.
Continuous waveform consists of a pure sine wave multiplied with a square wave that's either 0 or 1, corresponding to the keying of the carrier. Continuous waveform receive filters with passband around 500 Hz.