Which S3 storage class will meet these requirements MOST cost-effectively?

Explanations:

S3 Standard is designed for frequently accessed data. While it offers low latency and high throughput, it is not cost-effective for files that are rarely accessed.

S3 Standard-IA is intended for infrequently accessed data but requires immediate retrieval. It is more cost-effective than S3 Standard for this use case because it has lower storage costs and is still designed for rapid access when needed.

S3 Glacier Flexible Retrieval is designed for data that is not accessed frequently and has retrieval times ranging from minutes to hours. This does not meet the requirement for immediate retrieval and is not cost-effective for the given access pattern.

S3 Glacier Deep Archive is the lowest-cost storage option but is meant for long-term data that is rarely accessed, with retrieval times that can take hours. It does not meet the requirement for immediate access.