Which of the following is a Mac OS X feature that, when enabled, will automatically perform hourly backups for a period of 24 hours?

Using an external storage media, such as an external hard drive or Time Capsule, is required to enable Time Machine. When enabled, it will perform the following incremental or historical backups: hourly backups for the previous 24 hours, daily backups for the previous month, and weekly backups for all previous months. It's also worth noting that when your storage becomes full, the oldest backups are deleted.