AWS Cost Exploreris a tool that enables you to view and analyze your costs and usage. It provides an easy-to-use interface to visualize, understand, and manage AWS costs and usage over time. Cost Explorer allows the company to monitor ongoing costs, set budget alerts, and analyze cost drivers, which is ideal for keeping the cost of running an ecommerce website within a specific budget.

B. AWS SDKs: Incorrect, as they are software development kits that allow integration with AWS services but do not provide cost monitoring or management capabilities.

C. EC2 Image Builder: Incorrect, as it is a service for automating the creation of virtual machine images, not for monitoring costs.

D. AWS CloudFormation: Incorrect, as it is used for provisioning and managing infrastructure as code, not for cost monitoring.

AWS Cloud References:

AWS Cost Explorer