Your company is planning to set up an Azure subscription and an Azure tenant using Azure Active Directory. Does Azure Active Directory provide authentication services for services hosted in Azure and Microsoft Office 365?

Answer options:

A.Yes
B.No

Answer - A 
You can use Azure Active Directory to authenticate to both Azure-based resources and also to Microsoft office 365. 
The Microsoft documentation mentions the following. 

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