The correct answer is C, AWS Step Functions. This service is designed for building and coordinating serverless workflows. It allows you to orchestrate multiple AWS services, including AWS Lambda, into a single workflow. This makes it easier to manage complex, multi-step processes with features like conditional branching, error handling, and wait states. While AWS Lambda is a key component of serverless architecture, it is the execution service rather than the orchestration service. AWS Step Functions is specifically designed for the orchestration of serverless workflows, making it the best choice for this question.