Which AWS service requires the customer to patch the guest operating system?

Explanations:

AWS Lambda is a serverless compute service where users do not manage or patch the underlying infrastructure, including the guest operating system.

Amazon OpenSearch Service is a managed service where AWS handles the maintenance, including patching of the underlying operating system and infrastructure.

Amazon EC2 allows users to run virtual servers where they have full control over the guest operating system, including the responsibility for patching it.

Amazon ElastiCache is a managed caching service, where AWS takes care of the infrastructure and underlying systems, including OS patching.