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 – CPU based Scaling, the autoscaler is designed to maintain the target CPU utilization level by adjusting the number of instances based on the average usage of all vCPUs over time in the instance group. For instance, a target utilization of 60% means the autoscaler aims to keep the average CPU usage at 60% across the group. If the average exceeds this threshold, it adds more instances; if it's below, it may remove instances.

• Option A is incorrect because the scenario describes the autoscaler as being configured for CPU utilization, indicating it is not disabled.
• Option B is incorrect because the autoscaler acts immediately when the target utilization is met or exceeded, not after a delay.
• Option C is incorrect because if an instance were marked unhealthy by the load balancer, it would not receive traffic and might be replaced, but this does not directly relate to the autoscaler's decision to add instances based on CPU utilization.