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） server role， you find that the Enterprise CA option is not available. You need to install the AD CS server role as an Enterprise CA. What should you do first（）
- AAdd the DNS Server server role.
- BJoin the server to the domain.
- CAdd the Web Server （IIS） server role and the AD CS server role.
- DAdd the Active Directory Lightweight Directory Services （AD LDS） server role.