How Do AWS Users Trade Infrastructure Expenses for Operational Expenses

How do AWS users trade infrastructure expenses for operational expenses?

A) Secure their physical infrastructure to prevent malicious attacks.
B) Use AWS Budgets to ensure that spending on AWS resources does not exceed preset thresholds.
C) Eliminate the electricity costs that are associated with the hosting of physical servers.
D) Use AWS Auto Scaling to dynamically increase and decrease compute resources as needed.