Your network contains an Active Directory domain named contoso.com.
All servers run Windows Server 2012 R2.
The domain contains a domain controller named DC1 that is configured as an enterprise root
certification authority (CA).
All users in the domain are issued a smart card and are required to log on to their domain- joined
client computer by using their smart card.
A user named User1 resigned and started to work for a competing company.
You need to prevent User1 immediately from logging on to any computer in the domain.
The solution must not prevent other users from logging on to the domain.
Which tool should you use?

A.
Active Directory Users and Computers

B.
Active Directory Sites and Services

C.
The Certificates snap-in

D.
Server Manager

Explanation:
Disabling or enabling a user account
To open Active Directory Users and Computers, click Start, click Control Panel, double-click
Administrative Tools , and then double-click Active Directory Users and Computers .
To open Active Directory Users and Computers in Windows Server 2012, click Start , type dsa.msc .
In the console tree, click Users .
In the details pane, right-click the user.
Depending on the status of the account, do one of the following:
To disable the account, click Disable Account .
To enable the account, click Enable Account .