Answer: Cost Explorer

The correct answer is B, Cost Explorer. Cost Explorer is an AWS service that allows users to visualize, understand, and manage their AWS spending and usage over time. It provides pre-built reports, customizable filters, and visualizations to help analyze spending patterns, identify cost drivers, and track expenses over time. This service is specifically designed to review costs for services like Amazon EC2 and Amazon RDS, making it the appropriate tool for the company's needs as described in the question.

Author: LeetQuiz Editorial Team