The most cost-effective AWS service for orchestrating an ETL pipeline that maximizes performance is D. AWS Glue Workflows.
AWS Glue is a fully managed ETL service that makes it easy to move data between your data stores. AWS Glue simplifies and automates the difficult and time-consuming tasks of data discovery, conversion mapping, and job scheduling. AWS Glue Workflows allows you to orchestrate complex ETL jobs involving multiple crawlers, jobs, and triggers.
While the other services mentioned (Amazon EventBridge, Amazon MWAA, and AWS Step Functions) can be used for workflow orchestration, they are not specifically designed for ETL workloads and may not be as cost-effective for this use case. AWS Glue is designed for ETL workloads, and its workflows feature is specifically designed for orchestrating ETL jobs, making it the most suitable and cost-effective choice.