What is the MOST operationally efficient solution that meets these requirements?

Explanations:

This option requires the creation of a custom script and running it on each EC2 instance, which is not operationally efficient. It involves manual setup and maintenance for each instance, increasing complexity and overhead.

Using Amazon EventBridge to capture EC2 instance state changes and directly target an Amazon SNS topic is efficient and automated. It requires minimal setup, and notifications are sent directly without needing additional components or scripts.

While this option captures state changes with EventBridge, it involves an unnecessary AWS Lambda function as an intermediary to send notifications to SNS. This adds complexity and potential points of failure, making it less efficient than option B.

Although AWS Config can evaluate changes and trigger notifications, it is more complex than necessary for this requirement. This solution also introduces additional overhead with custom rules and remediation processes that are not required for simply notifying state changes.