Your company is using Microsoft Visual Studio App Center. They have a private distribution group that contains provisioned and un-provisioned devices. You have to distribute a new iOS application to the distribution group using App Center. 
Which of the following must they do?

Answer options:

A.Ensure to register the devices and sign the application.
B.Generate new .p12 files for each device.
C.Ensure to create a new active subscription.
D.Add each device owner to the collaborators group.

Answer – A 
When working with the distribution of apps, we have to ensure that we register the devices. 
This is also given in the Microsoft documentation. 

Since this is clearly mentioned, all other options are incorrect. 
For more information on auto-provisioning in Apps Center, please visit the following URL- 

https://docs.microsoft.com/en-us/appcenter/distribution/auto-provisioning