What is the name of the signal that contains the stereo audio and the 19kHz stereo pilot tone?

The correct answer is the composite signal. In the context of FM broadcasting, particularly for stereo transmissions, a composite signal is created by combining the main audio signal with additional information, such as the 19kHz stereo pilot tone. This pilot tone is essential as it helps stereo receivers identify and process the incoming signal properly, allowing them to separate left and right audio channels effectively.

A composite signal is essential in ensuring that the stereo audio can be transmitted over the same frequency channel, making efficient use of bandwidth while maintaining audio quality. It is a crucial component of FM stereo transmission standards, particularly in the context of analog broadcasting.

Baseband signals refer to audio or video signals that are not modulated for transmission but instead are the actual signals used in processing. Sideband signals refer to the portions of the modulated signal in radio transmission beyond the carrier frequency, and balanced signals typically relate to electrical characteristics rather than the audio format itself. Thus, these terms are relevant in their own contexts but do not apply directly to the question about stereo audio transmission.