问题：

[单选]

You are the network administrator for your company. All servers run Windows Server 2003. All servers are configured with static IP addresses. All client computers run Windows XP Professional. All client computers are configured as DHCP clients.The company has a main office and one branch office. The offices are separated by a router. A DHCP server is deployed in each office. The DHCP servers are named DHCP1 and DHCP2.  You configure scopes on the DHCP1 and DHCP2 as shown in the following table.

You shut down DHCP1 for scheduled maintenance. While DHCP1 is shut down， client computers in both offices continue to receive correct IP address assignments from DHCP2.  
You restart DHCP1. Several users report that when they restart their computers， they receive error messages stating that a duplicate IP address exists on the network.  
You need to ensure that these error messages do not appear when you shut down and restart a DHCP server. You need to ensure that changes you make does not affect the current DHCP functionality.
What should you do？（）

A . On each DHCP server， configure a superscope that includes both DHCP scopes.
B . Configure the router between the offices to block all broadcasts.
C . Modify the Main scope on DHCP1 to include addresses 10.1.16.0 through 10.1.27.254. Modify the Branch scope on DHCP2 to include addresses 10.2.16.0 through 10.2.27.254.
D . Modify the Main scope on DHCP2 to include addresses 10.1.16.0 through 10.1.31.254. Modify the Branch scope on DHCP1 to include addresses 10.2.16.0 through 10.2.31.254.