Your company has an Active Directory forest. You plan to install an Enterprise certification authority （CA） on a dedicated stand-alone server. When you attempt to add the Active Directory Certificate Services （AD CS） role， you find that the Enterprise CA option is not available. You need to install the AD CS role as an Enterprise CA. What should you do first（）

Add the DNS Server role.
B. Join the server to the domain.
C. Add the Web server （IIS） role and the AD CS role.
D. Add the Active Directory Lightweight Directory Service （AD LDS） role.