D. Reseating the RAM
Explanation:
The three loud, consecutive beeps during boot is a common error that indicates a problem with the computer's RAM (Random Access Memory). This error is caused by the computer not being able to properly access the RAM, which could be due to a loose or damaged connection. To remediate the issue, the technician should reseat the RAM by removing it, cleaning the contacts, and then reinstalling it. If reseating the RAM does not solve the issue, the technician should consider replacing the RAM with a new one. Replacing the power supply, UPS, or changing the CMOS battery may not solve the issue.