Final answer:
System files and applications can be excluded from Time Machine backups on a Mac by using the Time Machine preferences to customize which files and folders to exclude. This feature is always available, not only on weekdays.
Step-by-step explanation:
Can system files and applications be excluded from the backup? A) Yes, using Time Machine preferences is the correct answer. Time Machine, which is a backup software application included with macOS, allows users to select which files and folders are to be excluded from backups. This can be done by accessing Time Machine preferences and customizing the backup options to exclude particular system files, applications, or other data that you do not wish to back up. The option to exclude files applies at all times, irrespective of weekdays or weekends.