Your team has provisioned an Auto Scaling Groups in a single Region. The Auto Scaling Group at max capacity would total 40 EC2 instances between them. However, you notice that the Auto Scaling Groups will only scale out to a portion of that number of instances at any one time. What could be the problem

There is a vCPU-based on-demand instance limit per region.

Your AWS account has default quotas, formerly referred to as limits, for each AWS service. Unless otherwise noted, each quota is Region-specific. You can request increases for some quotas, and other quotas cannot be increased

Explanation:

b.. i believe would be the right one sorry if im wrong.