A user complains that their computer has become increasingly slow over time, especially when running multiple applications. After checking the system, you find that there's adequate disk space and no malware infections. Which of the following actions would be the BEST to take next to address this performance issue?
Defragment the system hard drive.
Downgrade the OS to an older version.
Add more RAM to the system.
Uninstall any applications that are not frequently used.