Final answer:
A differential and full backup would require no more than 2 backup sets as the full backup covers all files and the differential backup includes only the data changed since the last full backup.
Step-by-step explanation:
The type of backup that would require no more than 2 backup sets is the differential and full backup. With a full backup, all files and information are copied, providing a complete backup set. The differential backup then only needs to backup data that has changed since the last full backup. This means that to restore a system, you only need the last full backup and the last differential backup, which makes two backup sets in total.