What button must be pressed to monitor the "active" speakers?

To monitor the "active" speakers, the MAIN button is the correct choice. This button typically serves as the primary control for audio outputs in mixing and monitoring systems. When pressed, it directs the audio signals to the main output, allowing you to hear the sounds from the active speakers clearly. Monitoring through the MAIN button is essential for ensuring that the output levels are appropriate and that the sound mix is balanced before final output.

The other options, while related to various audio functions, do not specifically address the need to monitor the active speakers effectively. For instance, the CUT L+R might be used to mute certain channels, CTRL PGM could be focused on controlling program outputs rather than direct monitoring, and CR PLAY is often linked to playback functionalities rather than active monitoring. Thus, understanding the role of these buttons clarifies why the MAIN button is essential for monitoring purposes.