A user is trying to present a video in a conference room.

The correct answer is D. Verify the audio output assignment.

According to CompTIA A+ Core 1 220-1201 objectives under Hardware and Troubleshooting:

HDMI carries both video and audio signals. If video displays correctly but audio is not heard, it is often because the computer is still outputting sound to its internal speakers rather than the HDMI-connected device.

The user should check the audio output settings in the operating system and ensure the HDMI device (TV or projector) is selected as the audio output device.

Why the other options are incorrect:

A. Adjust the volume settings: Volumes are already at 50%, so adjusting them will not solve the problem if the audio output is assigned incorrectly.

B. Swap the HDMI cable: The video is working fine, so the cable is likely functional.

C. Reinsert the HDMI cable: Unlikely to resolve audio assignment issues if the connection is already working for video.