Your network consists of a single Active Directory forest that contains two domains named contoso.com and litwareinc.com. All domain controllers for contoso.com are in an office located in Singapore. All domain controllers for litwareinc.com are in an office located in Los Angeles. 
There is a single 128-Kbps WAN link between the two offices.All domain controllers run Windows Server 2003 Service Pack 2 （SP2） and are configured as DNS servers. Each domain controller contains a standard DNS zone for its respective domain.You need to ensure that users in the Singapore office can resolve IP addresses for servers in the Los Angeles office. The solution must minimize replication traffic over the WAN link. 
What should you do？（）

Your network contains a single Active Directory domain named contoso.com. The functional level of the domain is Windows 2000 mixed. 
You have a domain controller named DC1 that runs Windows Server 2003 Service Pack 2 （SP2）. DC1 hosts a standard primary zone for contoso.com. You need to ensure that only computers in the contoso.com domain can register host records in the contoso.com zone. 
What should you do？（）