You have a Windows Server 2008 R2 that has the Active Directory Certificate Services server role   installed.   You need to minimize the amount of time it takes for client computers to download a certificate revocation  list （CRL）. What should you do（）

• A、Install and configure an Online Responder.
• B、Install and configure an additional domain controller.
• C、Import the Root CA certificate into the Trusted Root Certification Authorities store on all client  workstations.
• D、Import the Issuing CA certificate into the Trusted Root Certification Authorities store on all client  workstations.