Which AWS tool assists in optimizing costs by providing insights on underutilized resources?

The correct answer is AWS Trusted Advisor. This tool plays a crucial role in optimizing costs by delivering insights on resource utilization, including identifying underutilized resources across your AWS infrastructure. Trusted Advisor analyzes your AWS account against best practices and provides recommendations that can help reduce costs, enhance performance, and improve security and fault tolerance.

AWS Budgets, while useful for tracking cost forecasts and setting spending limits, does not specifically identify underutilized resources. It focuses more on cost management and budget adherence.

AWS Cost Explorer allows users to visualize and analyze their AWS spending, providing detailed insights into historical and current costs to better understand spending patterns. However, it does not directly pinpoint underutilized resources like Trusted Advisor does.

The AWS Cost and Usage Report provides detailed information about usage and costs across AWS services but requires additional analysis to extract insights on underutilization. The report itself does not provide direct recommendations for optimization.

Therefore, AWS Trusted Advisor stands out as the proper tool for helping to optimize costs by identifying underutilized resources effectively.