What should you do?

You are the newly appointed enterprise administrator at Domain.com. The Domain.com network consists of a single Active Directory domain named Domain.com. All servers on the Domain.com network run Windows Server 2008.
Domain.com contains a domain controller named CERTKILLER-DC01 that runs mission critical services in the network. You are busy with the Restructuring of organizational unit domain
hierarchy and the deleting of unnecessary objects. However, you have received instructions from the CIO to do an Offline de-fragmentation of the active directory database without disrupting the mission critical services.
What should you do?

A.
The best option is to start CERTKILLER-DC01 in the Directory Services restore mode and run the defrag utility.

B.
The best option is to start CERTKILLER-DC01 in the Directory Services restore mode and run the Ntdsutil utility

C.
The best option is to stop the Domain controller service in the Services MMC and run the Ntdsutil utility

D.
The best option is to stop the Domain controller service in the Services MMC and run the Defrag utility.

Explanation:
You need to stop the Domain Controller service in the Microsoft Management Console (MMC) and then run the Ntdsutil tool. With this you can do offline defragmentation of the Active Directory database on CERTKILLER-DC01. Furthermore, the other mission critical services can continue running. You can use the restart feature of AD DS to stop AD DS so that you can perform the defragmentation of Active Directory objects.
Reference : Superior Identity Management Features in Windows Server 2008 Enterprise and Windows Server 2008 Datacenter / Directory Services: Active Directory Domain Services http://download.microsoft.com/download/8/2/f/82fa3808-7168-46f1-a07b- f1a7c9cb4e85/WS08%20Identity%20Management%20Features%20White%20Paper_FINAL.doc