What is the approximate bandwidth required to transmit a CW signal?

The correct choice reflects that Continuous Wave (CW) signals require a relatively narrow bandwidth. Typically, the approximate bandwidth needed to transmit a CW signal is around 150 Hz. This is because a CW signal produces keying tones that are generally not wide, allowing them to be efficiently transmitted over radio frequencies with minimal interference and distortion.

CW signals are used primarily in Morse code communications, which is a form of digital communication, and their frequency characteristics are well-suited to amateur radio practices. Given the limited frequency variation in a CW signal, the bandwidth remains low, typically around 150 Hz, which is optimal for clear transmission over long distances while maintaining the integrity of the signal.

The other options suggest much wider bandwidth requirements, which are unnecessary for CW signals, making them less accurate in representing the actual bandwidth requirements for this type of transmission.