Final answer:
VM scale sets are what let you create and manage a group of identical, load balanced VMs, supporting auto-scaling and high-availability for applications experiencing variable load.
Step-by-step explanation:
VM scale sets let you create and manage a group of identical, load balanced VMs. The correct answer to your question is A. VM scale sets. VM scale sets are an Azure compute resource that you can use to deploy and manage a set of identical VMs. With all VMs configured the same, VM scale sets are designed to support true auto-scaling, and they are particularly useful when you need to provide high-availability to your application, and you expect your application to experience variable load. Essentially, VM scale sets ensure that you can have your application continue to serve your users even as demands grow.