Your application currently uses customer keys which are generated via AWS KMS in the US east region. You now want to use the same set of keys from the EU-Central region. How can this be accomplished?

Answer options:

A.No need to do anything. AWS KMS automatically replicates keys to another region.
B.Use key rotation and rotate the existing keys to the EU-Central region.
C.Use the backing key from the US east region and use it in the EU-Central region.
D.Use multi-Region keys in AWS KMS.

Answer: D
AWS KMS supports multi-region keys, which are AWS KMS keys in different AWS Regions that can be used interchangeably – as though you had the same key in multiple Regions. With multi-Region keys, you can more easily move encrypted data between Regions without having to decrypt and re-encrypt with different keys in each Region.
Multi-Region keys are not global. You create a multi-Region primary key and then replicate it into Regions that you select within an AWS partition. Then you manage the multi-Region key in each Region independently. Neither AWS nor AWS KMS ever automatically creates or replicates multi-Region keys into any Region on your behalf. 
Option A is incorrect because neither AWS nor AWS KMS automatically replicates any keys into another Region. 
Option B is incorrect because key rotation cannot be used to export keys.
Option C is incorrect because the backing key cannot be used to export keys.
Option D is CORRECT because multi-Region keys have the capability to replicate keys from one AWS Region into another. 
For more information on KMS keys, kindly refer to the following URL:
https://aws.amazon.com/about-aws/whats-new/2021/06/kms-multi-region-keys/
https://docs.aws.amazon.com/kms/latest/developerguide/multi-region-keys-overview.html