The correct answer is 'Cold storage' because this type of storage tier is designed for data that is infrequently accessed and tolerates longer retrieval times, making it cost-effective for long-term storage needs. 'Hot storage' is incorrect as it is meant for frequently accessed data and comes with a higher cost. 'Multi-regional storage' relates to data availability across regions and doesn't imply lower costs for long-term storage. 'Glacier' is a specific service offered by AWS and not a storage tier category, which may mislead as the correct generalized choice for the scenario given.