You have a DNS server named Server1 that runs Windows Server 2003 Service Pack 2 （SP2）. Server1 hosts a primary zone for contoso.com. On Server1， you update the host （A） record for server2.contoso.com to have a new IP address.  On Server1， you run Ping server2.contoso.com from a command prompt and the old IP address for Server2 is returned.You need to ensure that the new IP address for Server2 resolves correctly on Server1. What should you do？（）

• A、Run Nbtstat –R.
• B、Run Ipconfig /flushdns.
• C、Restart the DNS Server service.
• D、Open the DNS snap-in， right-click on the server and click Clear Cache.