Option B is the best answer because AWS Budgets can take automated actions, and forecast-based thresholds let the company intervenebeforeactual spending fully lands. AWS documentation explains that AWS Budgets actions can target EC2 instances, and forecast-based budget alerts are specifically intended to warn when projected spend is expected to exceed the threshold during the period. That makes forecasted costs more proactive than waiting until actual spend reaches the full budgeted amount. Option A works, but it adds extra operational overhead by introducing SNS and Lambda when AWS Budgets actions can already automate the response directly. Option C is unrelated because a scheduled rule does not respond to budget state. Therefore, forecast-based AWS Budgets actions that automatically stop the EC2 instances is the most cost-effective and direct design. (AWS Documentation)

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