The correct answer is A. AWS Config can be used to identify resources that lack tags, and these resources can then be tagged programmatically. By leveraging tags in the backup plan, operational overhead is minimized as the process is automated. Option B involves a manual step of adding non-running resources to the backup vault, which increases operational overhead. Option C requires manual review by AWS account owners, which is also labor-intensive. Option D uses Amazon Inspector, which is primarily for security compliance, not for tagging and backing up resources efficiently.