A. You need to restore several word processing files that were accidentally deleted from My Documents.
C. You accidentally deleted several important e-mails from Outlook and need to restore them.
Explanation: You could use a backup to restore lost files and restore lost e-mails. Using a backup allows you to explicitly specify what content you want to restore.
Using a system image would be the appropriate way to restore a system after a hard disk failure. Using a restore point would be best suited to a situation where you've installed a misbehaving application or driver and need to revert the system to a prior state.
Hope this might help you.