Which AWS service allows you to automate operational tasks?

AWS Systems Manager is designed explicitly for automating operational tasks across your AWS resources. It provides a variety of features such as automation runbooks, which allow you to create automation workflows for routine operations, including software patching, configuration management, and compliance checks. This service centralizes operational data from multiple AWS services and enables you to automate common maintenance and deployment tasks, ultimately reducing the time and effort involved in managing your infrastructure.

In contrast, while Amazon CloudWatch is primarily focused on monitoring and logging, enabling users to track metrics and respond to alarms, it does not directly automate operational tasks. Amazon S3 is a storage service designed for storing and retrieving any amount of data at any time, while Amazon EC2 offers scalable computing capacity but does not provide specific tools for automating operational processes. AWS Systems Manager stands out as the service specifically tailored for automation, making it the best choice among the options provided.