Which AWS service or storage class will meet these requirements MOST cost-effectively?

Explanations:

Amazon FSx for Lustre is designed for high-performance computing with fast access to frequently accessed files, not for long-term archival storage.

Amazon EBS is optimized for primary storage of data for use with EC2 instances, with high performance but higher costs, not suited for cost-effective long-term storage.

Amazon EFS is a scalable file storage solution intended for active file storage and use with multiple EC2 instances, not for infrequently accessed, long-term archival data.

Amazon S3 Glacier Flexible Retrieval is optimized for long-term storage of infrequently accessed data, offering the most cost-effective option for data archiving and backup.