You have an Auto Scaling group with 2 AZs. One AZ has 4 EC2 instances, and the other has 3 EC2 instances. None of the instances are protected from scale in. Based on the default Auto Scaling termination policy, what will happen?

Answer options:

A.Auto Scaling selects an instance to terminate randomly.
B.Auto Scaling will terminate unprotected instances in the Availability Zone with the oldest launch configuration.
C.Auto Scaling terminates which unprotected instances are closest to the next billing hour.
D.Auto Scaling will select the AZ with 4 EC2 instances and terminate an instance.

Answer - D
The default termination policy is designed to help ensure that your network architecture spans Availability Zones evenly. When using the default termination policy, Auto Scaling selects an instance to terminate as follows.
Auto Scaling determines whether there are instances in multiple Availability Zones. If so, it selects the Availability Zone with the most instances and at least one instance that is not protected from scale in. If there is more than one Availability Zone with this number of instances, Auto Scaling selects the Availability Zone with the instances that use the oldest launch configuration.
For more information on Autoscaling instance termination, please refer to the below link:
http://docs.aws.amazon.com/autoscaling/latest/userguide/as-instance-termination.html