The correct answer is D because the Auto Scaler evaluates the average CPU utilization across all instances in the group, not just a single instance. According to GCP documentation on Auto Scaler and CPU-based Scaling, the autoscaler aims to maintain the target CPU utilization level by adjusting the number of instances based on the average usage of all vCPUs over time. If the average usage exceeds the target, the autoscaler adds more instances. For instance, a target of 0.75 (75%) means the autoscaler strives to keep the average CPU usage at 75% across the group. Option A is incorrect because the autoscaler is not disabled if it's configured for CPU utilization. Option B is incorrect as the autoscaler acts immediately upon reaching the target utilization. Option C is incorrect because an unhealthy instance would not serve traffic and might be replaced, not prevent scaling.