Enable hierarchical namespace on the storage account is correct.

Enable hierarchical namespace on the storage account turns on Azure Data Lake Storage Gen2 features which include POSIX style access control lists on directories and files and support for atomic directory and file operations. This feature therefore allows the team to apply access controls at the folder level and to perform directory operations atomically as the question requires.

Enable role based access control at the account level is incorrect because RBAC governs management and resource level permissions and does not provide POSIX style folder level ACLs or atomic directory semantics that are required for directory operations.

Configure replication to read access geo redundant storage RA GRS is incorrect because replication settings control data durability and cross region read access and they do not enable folder level access controls or atomic directory operations.

Change the storage account type to BlobStorage is incorrect because the BlobStorage account kind by itself does not enable the hierarchical namespace features needed for folder ACLs and atomic directory operations. ADLS Gen2 functionality requires the hierarchical namespace capability on a compatible storage account.

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