An errant process is known to use an entire processor and run at 100% CPU.

To detect CPU utilization issues within a 2-minute window, detailed monitoring is required. Basic monitoring publishes metrics at 5-minute intervals, which is too coarse to reliably detect a condition lasting only 2 minutes. Detailed monitoring publishes metrics at 1-minute granularity, allowing precise detection.

Amazon CloudWatch alarms support EC2 reboot actions directly, eliminating the need for custom Lambda functions. This minimizes administrative overhead and leverages native AWS integrations.

Options C and D introduce unnecessary complexity and delay. Option A cannot meet the timing requirement due to metric granularity.

Therefore, using a CloudWatch alarm with detailed monitoring and an EC2 reboot action is the correct solution.