You have an Active Directory domainthat runs Windows Server 2008 R2.
You need to implement a certification authority (CA) serverthat meets the following requirements:
Allows the certification authority to automatically issue certificates
Integrates with Active Directory Domain Services
What should you do?

A.
Install and configure the Active Directory Certificate Services server role as a Standalone Root CA.

B.
Install and configure the Active Directory Certificate Services server role as an Enterprise Root CA.

C.
Purchase a certificate from a third-party certification authority, Install and configure the Active Directory
Certificate Services server role as a Standalone Subordinate CA.

D.
Purchase a certificate from a third-party certification authority, Import the certificate into the computer store
of the schema master.

Explanation:
http://technet.microsoft.com/en-us/library/cc776874%28v=ws.10%29.aspx
Enterprise certification authorities
The Enterprise Administrator can install Certificate Services to create an enterprise certification authority (CA).
Enterprise CAs can issue certificates forpurposes such as digital signatures, secure e-mailusing S/MIME
(Secure Multipurpose Internet Mail Extensions), authentication to a secure Web server using Secure Sockets
Layer (SSL) or Transport Layer Security (TLS) and logging on to a Windows Server 2003 family domain using a
smart card.
An enterprise CA has the following features:
An enterprise CA requires the Active Directory directory service.
When you install an enterprise root CA, it usesGroup Policy to propagate its certificate to the Trusted
Root Certification Authorities certificate store for all users and computers in the domain. You must be a
Domain Administrator or be an administrator with write access to Active Directory to install an enterprise
root CA.
Certificates can be issued for logging on to a Windows Server 2003 family domain using smart cards.
The enterprise exit module publishes user certificates and the certificate revocation list (CRL) to Active
Directory. In order to publish certificates to Active Directory, the server that the CA is installed on must be a
member of the Certificate Publishers group. This isautomatic for the domain the server is in, but theserver
must be delegated the proper security permissions to publish certificates in other domains. For more
information about the exit module, see Policy and exit modules.
An enterprise CA uses certificate types, which are based on a certificate template. The following functionality is
possible when you use certificate templates:
Enterprise CAs enforce credential checks on users during certificate enrollment. Each certificate template
has a security permission set in Active Directory that determines whether the certificate requester is
authorized to receive the type of certificate they have requested.
The certificate subject name can be generated automatically from the information in Active Directory or
supplied explicitly by the requestor.
The policy module adds a predefined list of certificate extensions to the issued certificate. The extensions
are defined by the certificate template. This reduces the amount of information a certificate requester has to
provide about the certificate and its intended use.
http://technet.microsoft.com/en-us/library/cc780501%28WS.10%29.aspx
Stand-alone certification authorities
You can install Certificate Services to create a stand-alone certification authority (CA). Stand-aloneCAs can
issue certificates for purposes such as digital signatures, secure e-mail using S/MIME (Secure Multipurpose
Internet Mail Extensions) and authentication to a secure Web server using Secure Sockets Layer (SSL) or
Transport Layer Security (TLS).
A stand-alone CA has the following characteristics:
Unlike an enterprise CA, a stand-alone CA does not require the use of the Active Directory directory
service. Stand-alone CAs are primarily intended to be used as Trusted Offline Root CAs in a CA hierarchy
or when extranets and the Internet are involved. Additionally, if you want to use a custom policy module for a
CA, you would first install a stand-alone CA and then replace the stand-alone policy module with your
custom policy module.
When submitting a certificate request to a stand-alone CA, a certificate requester must explicitlysupply all
identifying information about themselves and the ty pe of certificate that is wanted in the certificaterequest.
(This does not need to be done when submitting a request to an enterprise CA, since the enterprise user’s
information is already in Active Directory and the certificate type is described by a certificate template). The
authentication information for requests is obtainedfrom the local computer’s Security Accounts Manager
database.
By default, all certificate requests sent to the stand-alone CA are set to Pending until the administrator of
the stand-alone CA verifies the identity of the requester and approves the request. This is done for security
reasons, because the certificate requester’s credentials are not verified by the stand-alone CA.
Certificate templates are not used.
No certificates can be issued for logging on toa Windows Server 2003 family domain using smart cards,
but other types of certificates can be issued and stored on a smart card.
The administrator has to explicitly distribute the stand-alone CA’s certificate to the domain user’s trusted
root store or users must perform that task themselves.
When a stand-alone CA uses Active Directory, it hasthese additional features:
If a member of the Domain Administrators group or an administrator with write access to Active Directory,
installs a stand-alone root CA, it is automatically added to the Trusted Root Certification Authorities
certificate store for all users and computers in the domain. For this reason, if you install a stand-alone root
CA in an Active Directory domain, you should not change the default action of the CA upon receiving
certificate requests (which marks requests as Pending). Otherwise, you will have a trusted root CA that
automatically issues certificates without verifyingthe identity of the certificate requester.
If a stand-alone CA is installed by a member ofthe Domain Administrators group of the parent domain of
a tree in the enterprise, or by an administrator with write access to Active Directory, then the stand-alone CA
will publish its CA certificate and the certificaterevocation list (CRL) to Active Directory.