An administrator needs to back up changed files only and has time constraints on the back up window. Which of the following is the BEST choice for a backup strategy?

A differential backup targets only files that have changed since the last full backup, satisfying the requirement to skip unchanged data and stay within a constrained backup window. Restoration requires only two sets - the last full backup plus the most recent differential - making recovery fast and predictable compared to chaining multiple incremental sets.

A snapshot captures a point-in-time system state, but is not a file-level backup strategy designed for scheduled backups of only changed files.

A full backup copies every file regardless of whether it changed, consuming the most time and storage - directly conflicting with the time constraint requirement.

An incremental backup captures only files changed since the last backup of any type, minimizing each individual backup but building a long chain of sets that significantly increases restore complexity and time.