The correct answer is C, AWS Key Management Service (KMS). AWS KMS is a managed service that enables the creation and control of encryption keys for securing data in various AWS services, including Amazon EBS. It provides a secure and resilient service that uses hardware security modules validated under FIPS 140-2 to protect your keys. When using Amazon EBS, you can encrypt the data at rest by selecting AWS KMS as the key management option. This ensures that the data stored on the EBS volumes remains secure and encrypted. AWS KMS integrates seamlessly with Amazon EBS and provides a robust key management infrastructure.