You have an enterprise subordinate certification authority (CA). The CA issues smart card logon  certificates.   Users are required to log on to the domain by using a smart card.   Your companys corporate security policy states that when an employee resigns, his ability to log on to the network must be immediately revoked.   An employee resigns.   You need to immediately prevent the employee from logging on to the domain.  What should you do（）

• A、Revoke the employees smart card certificate.
• B、Disable the employees Active Directory account.
• C、Publish a new delta certificate revocation list （CRL）.
• D、Reset the password for the employees Active Directory account.