The correct answer is C. Budgets in Azure Cost Management and Billing are specifically designed to track and manage costs associated with Azure resources. Budgets allow you to set spending thresholds and receive alerts when spending reaches these thresholds, providing detailed cost reports and helping in cost optimization. While tags can help categorize resources, and usage and quotas can help monitor resource consumption, neither are as effective for directly tracking costs. Hence, 'budgets' is the most appropriate tool for tracking Azure resource costs.