A company is optimizing its AWS costs.

The condition is deterministic: maximum CPU utilization must be below 2% for the previous 24 one-hour periods. That requires a static threshold, not anomaly detection. Anomaly detection learns a normal band from historical behavior, which is useful for unusual patterns but not for a fixed business definition of “idle.” CloudWatch alarms use “Datapoints to Alarm” as an M-out-of-N evaluation model, so 24 out of 24 means all 24 hourly datapoints must breach the threshold. AWS also documents idle-instance alarm examples based on CPU utilization staying below a threshold for 24 consecutive periods. Option D would alarm if only one hour was below 2%, which is far too sensitive. Options A and C use the wrong threshold type.

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