Answer: C.
Option A is INCORRECT because it is not a service for decoupling use-case.
AWS Auto Scaling adjusts the capacity to maintain performance leaving unchanged the application design.
Option B is INCORRECT because AWS ELB is a service to distribute the workload across EC2 instance, not a service to support application refactoring or re-engineering.
Option C is CORRECT because Amazon SQS implements messaging that is a typical integration pattern to decouple application components.
AWS documentation mentions "Amazon SQS offers a reliable, highly-scalable hosted queue for storing messages as they travel between applications or microservices.
It moves data between distributed application components and helps you decouple these components".
Option D is INCORRECT because it is a streaming service not suitable for the scenario.