A company is planning to host an application on a set of Virtual Machines. The Virtual Machines are going to be running for a longer period. Which of the following should be considered to reduce the overall cost of Virtual Machine usage?

Answer options:

A.Premium Disks
B.Virtual Machine Scale sets
C.Azure Reservations
D.Azure Resource Groups

Answer – C 
The Microsoft documentation mentions the following. 

Option A is incorrect since using Premium Disks is an expensive option. 
Option B is incorrect since this is used for scalability of your virtual machines. 
Option D is incorrect since this is used for grouping your Azure resources. 
For more information on Azure Cost Reservations, please visit the below URL- 

https://docs.microsoft.com/en-us/azure/billing/billing-save-compute-costs-reservations