A company has deployed a web application in a VPC that has subnets in three Availability Zones. The company launches three Amazon EC2 instances from an EC2 Auto Scaling group behind an Application Load Balancer (ALB).
A SysOps administrator notices that two of the EC2 instances are in the same Availability Zone, rather than being distributed evenly across all three Availability Zones. There are no errors in the Auto Scaling group's activity history.
What is the MOST likely reason for the unexpected placement of EC2 instances?

A. One Availability Zone did not have sufficient capacity for the requested EC2 instance type.
B. The ALB was configured for only two Availability Zones.
C. The Auto Scaling group was configured for only two Availability Zones.
D. Amazon EC2 Auto Scaling randomly placed the instances in Availability Zones.