AWS Cost Explorer is the correct choice because it provides interactive visualizations and reports that let Alpine Transit review spending trends over time, break down costs by AWS service and by linked account, and identify the primary cost drivers across the environment.

AWS Cost Explorer exposes historical charge data with filtering and grouping by service, account, and tags and it supports trend charts, forecasting, and detailed breakdowns so teams can pinpoint which services or accounts are causing the most spend.

AWS Pricing Calculator is not correct because it is intended for estimating future costs before deployment and it does not analyze actual past charges or provide interactive trend visualizations.

AWS CloudTrail is not correct because it records API activity for auditing and security and it does not provide consolidated cost analytics or spending breakdowns.

AWS Organizations consolidated billing is not correct because it centralizes and aggregates billing across accounts for payment and account management and it does not offer the interactive cost reporting and driver analysis that Cost Explorer delivers.

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