The correct answer is C: S3 Standard-Infrequent Access (S3 Standard-IA). This storage class is designed for data that is accessed less frequently but still requires rapid access when needed. It offers high durability, high throughput, and low latency similar to S3 Standard, but at a lower cost for storage. S3 Standard-IA is ideal for long-term storage, backups, and as a data store for disaster recovery files. It is the most cost-effective option for the company's requirements because it provides the necessary availability and performance while being more affordable than S3 Standard. S3 One Zone-IA, while cheaper, is not suitable for critical data that cannot be recreated, as it is stored in a single Availability Zone and is at a higher risk of data loss. S3 Glacier is not the best fit due to its retrieval times which are typically within hours, not seconds.