You are the network administrator for Alpine Ski House.……

You are the network administrator for Alpine Ski House. The network consists of a single Active Directory forest that contains five domains. The functional level of the forest is Windows 2000. You have not configured any universal groups in the forest. One domain is a child domain named  child1.alpineskihouse.com  that contains two domain controllers and 50 client computers. The functional level of the domain is Windows Server 2003. The network includes an Active Directory site named Site1 that contains two domain controllers. Site1 represents a remote clinic, and the location changes every few months. All of the computers in child1.alpineskihouse.com are located in the remote clinic. The single WAN connection that connects the remote clinic to the main network is often saturated or unavailable. Site1 does not include any global catalog servers. You create several new user accounts on the domain controllers located in Site1. You need to ensure that users in the remote clinic can always quickly and successfully log on to the domain. 
What should you do?（）

A. Enable universal group membership caching in Site1.
B. Add the HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\Lsa\IgnoreGCFailures key to the registry on both domain controllers in Site1.
C. Add the HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\Lsa\IgnoreGCFailures key to the registry on all global catalog servers in the forest.
D. Raise the functional level of the forest to Windows Server 2003.