Your company is planning to set up an Azure subscription and an Azure tenant using Azure Active Directory. Would the company need to implement domain controllers on Azure virtual machines to use the Azure AD service?

Answer options:

A.Yes
B.No

Answer - B 
Azure Active Directory is a completely managed service. You don’t need to provision any infrastructure to implement Azure Active Directory. 
For more information on Azure Active Directory, please visit the below URL- 

https://docs.microsoft.com/en-us/azure/active-directory/fundamentals/active-directory-whatis