Which AWS service will meet this requirement with MINIMAL operational effort?

Explanations:

While Amazon S3 can store backups, it does not provide a centralized management solution for automating backups from EC2 and EFS. Manual processes would still be required to manage backups effectively.

AWS Data Pipeline is a service for processing and moving data between different AWS services. It does not specifically focus on automating backups for EC2 instances or EFS, making it unsuitable for centralized backup management.

AWS Backup is designed specifically for centralized management of backups across AWS services, including Amazon EC2 and Amazon EFS. It automates the backup process, allowing for minimal operational effort to configure and manage backups.

AWS Storage Gateway is primarily used for hybrid cloud storage solutions, enabling on-premises applications to use cloud storage. It does not provide a dedicated backup management service for EC2 or EFS, making it an inappropriate choice for this requirement.