What kind of audio mix is provided back to a telephone caller?

The correct choice is a mix-minus, which is specifically designed for situations where a caller on the telephone needs to hear the program's audio without hearing their own voice echoed back to them. A mix-minus setup feeds the caller the audio from the show or event they're participating in, but omits their own voice from that audio mix. This prevents confusion and feedback that could occur if they were to hear their own voice in real-time on the line, which would lead to delays and an unpleasant experience.

In contrast, a full mix would include all audio elements, including the caller's own voice, leading to potential echoes and distractions. A stereo mix is typically used for music or more complex audio situations where left and right channels provide a richer experience but may not be suitable for communication purposes, especially over the phone. A mono mix, while simple and straightforward, does not provide the separation that is advantageous in a telephone communication context where a mix-minus is required to ensure clarity and ease of conversation.