Which of the below-given service could be used in the AWS cloud for the management of encryption keys?

Answer options:

A.Amazon Inspector
B.Amazon Cognito
C.CloudHSM
D.Amazon GuardDuty

Answer: C
CloudHSM (HSM stands for Hardware Security Module) helps in the management of encryption keys. Standards compliant CloudHSM is a fully-managed service.
Option A is INCORRECT. Amazon Inspector helps improve the security and compliance adherence of the applications deployed on the AWS cloud.
Option B is INCORRECT. Amazon Cognito is an AWS service for developers that simplifies user sign-up and sign-in to their developed mobile apps and web apps.
Option C is CORRECT. Refer to the explanation above.
Option D is INCORRECT. Amazon GuardDuty performs continuous monitoring to protect AWS account, S3 data and workloads from any malicious, unauthorized activities.
Reference: 
https://aws.amazon.com/inspector/
https://aws.amazon.com/cognito/
https://aws.amazon.com/cloudhsm/
https://aws.amazon.com/guardduty/