The correct choice is Amazon EFS Infrequent Access because the lab needs a POSIX compliant file system and the archives are read only a few days per year so lower storage cost for cold files is the priority.

Amazon EFS Infrequent Access gives a native POSIX and NFS mountable file system so existing workflows can read files without changes and lifecycle management moves seldom accessed files to lower cost storage while preserving access semantics. This combination delivers the needed file system behavior and much lower storage charges for data that is rarely accessed.

Amazon EFS Standard does meet the POSIX requirement but it charges active storage rates for all files so it is less cost effective for archives that sit idle most of the year.

Amazon S3 Standard-IA provides lower cost object storage for infrequent access but it is not a POSIX file system and using it would require object APIs or a gateway which adds complexity and may not satisfy a direct mount requirement.

Amazon S3 Standard is general purpose object storage with higher availability and frequent access pricing and it does not provide a native POSIX interface so it does not meet the functional requirement.

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