The SysOps administrator must monitor inter-Region data transfer spending and notify an email distribution list when transfer costs reach 75% of a predefined threshold. Which approach meets these requirements?

AWS Budgets is the most suitable service for this requirement because it allows you to set custom budgets to track your cost and usage, including specific services like data transfer. You can configure alerts to notify you when actual or forecasted costs exceed your defined thresholds, such as 75% of a budget, and send these notifications directly to an Amazon SNS topic or email address. The other options are less efficient or appropriate. Producing an AWS Cost and Usage Report and querying it in Athena is a valid way to analyze costs, but it's not designed for real-time threshold-based alerting. An Amazon CloudWatch billing alarm can monitor overall billing, but AWS Budgets offers more granular control over specific cost categories like data transfer. Capturing VPC Flow Logs and processing them with a Lambda function is overly complex and resource-intensive for a task that AWS Budgets handles natively.