A SysOps Administrator has implemented an Auto Scaling group with a step scaling policy. The Administrator notices that the additional instances have not been included in the aggregated metrics.
Why are the additional instances missing from the aggregated metrics?

A. The warm-up period has not expired
B. The instances are still in the boot process
C. The instances have not been attached to the Auto Scaling group
D. The instances are included in a different set of metrics