Your network consists of one Active Directory domain that contains two servers that run Windows
Server 2008 named Server1 and Server2. Server1 runs Active Directory Certificate Services (AD CS)
and is configured as a certification authority (CA). Server2 runs Internet Information Services (IIS)
and hosts a secure Web service. External users must subscribe in order to access the Web service.
The Web service accepts subscriptions only from client computers that run Windows XP Service Pack
2 or Windows Vista. The relevant portion of the network is configured as shown in the following
diagram.

You need to ensure that subscribers can successfully connect to the Web service on Server2 through
HTTPS. Users must not receive any certificate-related errors. What should you do on Server2?

A.
Install a server certificate issued by Server1.

B.
Issue and install a self-signed server certificate.

C.
Install a server certificate issued by a public CA.

D.
Install the trusted root CA certificate issued by Server1.

Explanation:
To ensure that the subscribers can successfully connect to the Web service on Server2 through
HTTPS without receiving any certificate errors, you need to install a server certificate issued by a
public CA. This is because a web service needs, that is not internal application of the company needs
to be accessed by the external users on the Internet server. Public Certificates are usually used
where services needs to be accessed on the Internet as in the above case on Server2 that runs
Internet Information Services (IIS) and hosts a secure Web service. The most common use of the

certificates granted by a public (that is, external) CA on the Internet is probably by sites doing ecommerce. The certificates issued by Public CA are most commonly used by a site to identify itself to
the public and provide secure communications during financial and other sensitive transactions.
Certificates (or digital IDs) are used to verify the identity of a Web site and provide a secure
communications channel for transactions that may contain sensitive information. Digital certificates
can also be used by the news media or other sources of information to validate their identity, and
therefore the integrity of the provided data.
Certificate Server / Public CA
http://www.windowsitlibrary.com/Content/405/17/1.html