You need to ensure that the application deployment meets the following requirements:

Your network consists of a single Active Directory domain. All domain controllers run Windows Server 2008 R2.

All client computers run Windows 7. All user accounts are stored in an organizational unit (OU) named Staff. All client computer accounts are stored in an OU named Clients. You plan to deploy a new application.

You need to ensure that the application deployment meets the following requirements:

Users must access the application from an icon on the Start menu.
The application must be available to remote users when they are offline.

What should you do?

A.
Publish the application to users in the Staff OU.

B.
Publish the application to users in the Clients OU.

C.
Assign the application to computers in the Staff OU.

D.
Assign the application to computers in the Clients OU.

Explanation:
http://www.youtube.com/watch?v=hQkRN96cKkM

Group policy objects can be applied either to users or to computers. Deploying applications through the Active Directory is also done through the use of group policies, and therefore applications are deployed either on a per user basis or on a per computer basis.

There are two different ways that you can deploy an application through the Active Directory. You can either publish the application or you can assign the application. You can only publish applications to users, but you can assign applications to either users or to computers. The application is deployed in a different manner depending on which of these methods you use.

Publishing an application doesnt actually install the application, but rather makes it available to users. For example, suppose that you were to publish Microsoft Office. Publishing is a group policy setting, so it would not take effect until the next time that the user logs in. When the user does log in though, they will not initially notice anything different. However, if the user were to open the Control Panel and click on the Add / Remove Programs option, they will find that Microsoft Office is now on the list. A user can then choose to install Microsoft office on their machine.

One thing to keep in mind is that regardless of which deployment method you use, Windows does not perform any sort of software metering. Therefore, it will be up to you to make sure that you have enough licenses for the software that you are installing.

Assigning an application to a user works differently than publishing an application. Again, assigning an application is a group policy action, so the assignment wont take effect until the next time that the user logs in. When the user does log in, they will see that the new application has been added to the Start menu and / or to the desktop.

Although a menu option or an icon for the application exists, the software hasnt actually been installed though. To avoid overwhelming the server containing the installation package, the software is not actually installed until the user attempts to use it for the first time.

This is also where the self healing feature comes in. When ever a user attempts to use the application, Windows always does a quick check to make sure that the application hasnt been damaged. If files or registry settings are missing, they are automatically replaced.

Assigning an application to a computer works similarly to assigning an application to a user. The main difference is that the assignment is linked to the computer rather than to the user, so it takes effect the next time that the computer is rebooted. Assigning an application to a computer also differs from user assignments in that the deployment process actually installs the application rather than just the applications icon.

as assigning installs the application the next time a computer reboots teh app will be availible when at next login regardless of which user logs in. also as its being assigned to a cpmputer teh GPO needs to be linked to the Clients OU as this is where teh computer accounts are located.

Assigning Software to a group.
http://support.microsoft.com/kb/324750

Create a folder to hold the Windows Installer package on a server. Share the folder by applying permissions that let users and computers read and run these files. Then, copy the MSI package files into this location.
From a Windows Server 2003-based computer in the domain, log on as a domain administrator, and then start Active Directory Users and Computers.
In Active Directory Users and Computers, right-click the container to which you want to link the GPOs, and then click Properties.
Click the Group Policy tab, and then click New to create a new GPO for installing the Windows Installer package. Give the new GPO a descriptive name.
Click the new GPO, and then click Edit.

The Group Policy Object Editor starts.
Right-click the Software Settings folder under either Computer Configuration or User Configuration, point to New, and then click Package.