An organization manages accounts with AWS Organizations and needs a backup strategy for all EC2 instances across every account. The approach should be the most operationally efficient way to apply backups company-wide. Which solution meets this requirement?

The correct answer is to use AWS Backup from the management account. AWS Backup is a centralized, fully managed backup service that allows you to configure backup policies and apply them across multiple AWS services and accounts within an AWS Organizations setup. This approach is the most operationally efficient because it centralizes backup management, reducing the need for individual configurations in each account. Deploying Lambda functions in each account is less efficient due to the overhead of managing and deploying the function across many accounts. CloudFormation StackSets can tag instances, but tagging alone doesn't create backups; it would require another service to act on those tags. Service Control Policies (SCPs) restrict actions but cannot initiate or trigger actions like scheduled snapshots.