The correct option is Amazon EC2 Auto Scaling adds only 1 instance to the group. The Auto Scaling group has a maximum size of 5 and a current size of 4 so the policy cannot increase the group beyond its configured maximum.

The scale-out policy would compute a desired capacity of 8 when adding 4 instances to the current 4 but Amazon EC2 Auto Scaling enforces the group's maximum and clamps the desired capacity to 5. As a result the group launches only one additional instance to reach the maximum.

Amazon EC2 Auto Scaling adds 4 instances to the group is incorrect because Auto Scaling never launches more instances than the group's configured maximum. The service applies the max limit before provisioning new instances.

Amazon EC2 Auto Scaling launches 4 instances and then scales in 3 shortly afterward is incorrect because Auto Scaling does not overprovision beyond the maximum and then immediately terminate excess instances. The limit is enforced up front rather than by launching and then removing instances.

Amazon EC2 Auto Scaling adds 4 instances across multiple Availability Zones because the maximum size applies per Availability Zone is incorrect because the maximum size in this Auto Scaling group is enforced at the group level and not as a per Availability Zone maximum in this scenario.

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