A company wants to implement Azure Multi-Factor Authentication. Which of the following is the recommended policy?

Answer options:

A.Enable per-user
B.Enable per-session
C.Enable Conditional Access
D.Enable Security Defaults

Answer: C 
Option A is incorrect as it is not advised per user, as it would be time consuming and difficult to maintain for large number of users 
Option B is incorrect because session is per user login and policy is not applied on user session 
Option C is CORRECT because it would help to provide the access for group of users and helps in managing efficiently 
Option D is incorrect because it is applicable for free tier by default 
Diagram:

Reference:

https://docs.microsoft.com/en-us/azure/active-directory/authentication/howto-mfa-userstates