Answer: Amazon EC2 Auto Scaling

The correct answer is D, Amazon EC2 Auto Scaling. This service automatically adjusts the number of EC2 instances in response to demand, ensuring steady and predictable performance while optimizing costs. It allows for scaling out (adding more instances) during high demand and scaling in (removing instances) during low demand. Amazon CloudWatch (A) is a monitoring service and does not provide automatic scaling. The Application Load Balancer (B) helps distribute traffic but does not manage instance scaling. AWS Batch (C) is for running batch jobs and does not offer the same scaling capabilities as EC2 Auto Scaling.

Author: LeetQuiz Editorial Team