Which AWS service can send notifications when a specific Amazon CloudWatch alarm is triggered?

Amazon Simple Notification Service (SNS) is the correct choice because it is a fully managed messaging service that enables you to send notifications from the cloud. CloudWatch alarms can be configured to publish messages to an SNS topic when the alarm state changes, triggering notifications to subscribers (e.g., email, SMS, or other AWS services). AWS CloudTrail is incorrect because it records API calls and related events in your AWS account, primarily for auditing and security, not for sending real-time notifications from alarms. Amazon Simple Queue Service (SQS) is incorrect as it is a message queuing service used for decoupling and scaling microservices, distributed systems, and serverless applications, not for direct notification delivery from alarms. Amazon EventBridge (formerly CloudWatch Events) is incorrect because while it can react to events and trigger actions, SNS is specifically designed and commonly used for the direct notification aspect of CloudWatch alarms.