The correct answer is A because creating a snapshot and then a new disk from that snapshot in the target zone is the most straightforward method to replicate a disk across zones. This approach is supported by Google Cloud Platform's documentation, which states that disks are zonal resources and their contents can be moved to a different zone by snapshotting the disk and creating a new disk from the snapshot in the desired zone.

• Option B is incorrect because it moves the instance rather than creating a replica.
• Option C is possible but involves unnecessary steps, making it less efficient.
• Option D is incorrect as gcloud does not support directly copying a disk to a different zone.