You have a Microsoft 365 subscription and Microsoft 365 E5 licenses assigned to your users. You need to enforce all your users to register for Multi-Factor authentication. Where should you configure this? 

Answer options:

A.Azure Active Directory – Multi-Factor Authentication – Server settings
B.Azure Active Directory – User settings – User features
C.Azure Active Directory – Password reset – Administrator Policy
D.Identity Protection – MFA registration policy

Correct Answer: D 
You should create a MFA registration policy that will prompt the users to register for multi-factor authentication. They will have 14 days to complete the registration. 

Option A is incorrect. This is where you configure the timeout period for two-way text messages for on premise MFA server.
Option B is incorrect. This is where you can set certain user experience configurations. Not related to MFA authentication.
Option C is incorrect. This is where you can configure MFA settings scoped at users with administrator roles, such as number of methods required to reset password and authentication methods available.
Reference: 
To know more about the MFA registration policy, please refer to the link below: 

https://docs.microsoft.com/en-us/azure/active-directory/identity-protection/howto-identity-protection-configure-mfa-policy