The most efficient solution for this scenario is to use EC2 Auto Scaling lifecycle hooks to run a custom script to send data to the audit system when instances are launched and terminated. The lifecycle hook can be used to delay instance termination until the script has completed, ensuring that all data is sent to the audit system before the instance is terminated. This solution is more efficient than using a scheduled AWS Lambda function, which would require running the function periodically and may not capture all instances launched and terminated within the interval. Running a custom script through user data is also not an optimal solution, as it may not guarantee that all instances send data to the audit system. Therefore, option B is the correct answer.

Use EC2 Auto Scaling lifecycle hooks to run a custom script to send data to the audit system when instances are launched and terminated

EC2 Auto Scaling lifecycle hooks allow you to perform custom actions as instances launch and terminate. This is the most efficient way to trigger the auditing script execution at instance launch and termination.

https://docs.aws.amazon.com/autoscaling/ec2/userguide/lifecycle-hooks.html

Amazon EC2 Auto Scaling offers the ability to add lifecycle hooks to your Auto Scaling groups. These hooks let you create solutions that are aware of events in the Auto Scaling instance lifecycle, and then perform a custom action on instances when the corresponding lifecycle event occurs. (https://docs.aws.amazon.com/autoscaling/ec2/userguide/lifecycle-hooks.html)

it is B. read this: https://docs.aws.amazon.com/autoscaling/ec2/userguide/lifecycle-hooks.html