The correct answers areA, C, and Ebecause the company needs a fully managed solution forSFTP uploads to Amazon S3, followed byautomatic decryptionandmovement of files to another directorywithminimal operational overhead.AWS Transfer Familyis the best fit because it provides a managed SFTP endpoint directly integrated with Amazon S3. Configuring the S3 bucket as the home directory enables customers to upload files without the company needing to manage its own file transfer servers.

The requirement to avoid separate authentication services and minimize operational work is well served by nativeAWS Transfer Family workflows. A workflow can automatically run post-upload steps on files as they arrive. TheDECRYPTaction is specifically designed to decrypt uploaded encrypted files as part of the managed workflow. After decryption, theCOPYaction can place the processed file into the second directory in the same S3 bucket for downstream processing.

Option B is less appropriate because using S3 events and Lambda adds custom orchestration where a native Transfer Family workflow already handles the need more simply. Option D is incorrect because polling with an external script introduces unnecessary infrastructure and operational overhead. Option F is also incorrect because AWS Batch polling and custom decryption logic is far more complex than a managed file-transfer workflow.

AWS best practices favor managed services and native workflow features to reduce custom code and infrastructure management. Therefore, the best solution is to useAWS Transfer Family for SFTP uploads, along withTransfer Family workflow DECRYPTandCOPYactions to automate the full post-upload process.