Which of the following is an example of periodic maintenance for a computer system?

Periodic maintenance for a computer system involves routine tasks aimed at optimizing performance and ensuring reliability over time. System backup is a critical component of this maintenance as it involves creating copies of the system's data to protect against data loss due to failures, accidents, or other unforeseen issues. Regular backups help ensure that critical information can be restored if necessary, making it an essential part of maintaining a healthy computing environment.

In contrast, while manual checking and exception tracking are important tasks for monitoring system performance and identifying issues, they do not typically fall into the category of periodic maintenance specifically aimed at preventive measures. Defragmentation, although beneficial for performance optimization by reorganizing fragmented data on the disk, may also not be performed as frequently as backups, making system backup the more appropriate example of periodic maintenance.