A SysOps administrator needs to encrypt an existing Amazon Elastic File System (Amazon EFS) file system by using an existing AWS KMS customer managed key. Which solution will meet these requirements?

Amazon EFS replication can be used to replicate data from an existing unencrypted file system to a new encrypted file system. By specifying an existing KMS customer managed key during the creation of the destination (replica) file system, all data and metadata are copied in an encrypted state, effectively migrating to an encrypted EFS file system without manual data transfer steps.

Amazon EFS does not support directly modifying an existing file system to enable encryption at rest; encryption can only be enabled at file system creation time, making in-place encryption impossible.

This option is incorrect because it does not properly specify the use of the existing KMS customer managed key or uses an incorrect replication configuration that does not meet the encryption requirements as stated.

While creating a new encrypted EFS file system with a KMS customer managed key is a valid starting point, this option relies on a manual data copy process (e.g., AWS DataSync or rsync) rather than the more seamless EFS replication feature, making it less optimal compared to option A.