Your network contains an Active Directory-integrated DNS zone named contoso.com.
You discover that the zone includes DNS records for computers that were removed from the
network.
You need to ensure that the DNS records are deleted automatically from the zone.
What should you do?

A.
From DNS Manager, set the aging properties.

B.
Create a scheduled task that runs dnslint.exe /v /d contoso.com.

C.
From DNS Manager, modify the refresh interval of the start of authority (SOA) record.

D.
Create a scheduled task that runs ipconfig.exe /flushdns.

Explanation:
http://technet.microsoft.com/en-us/library/cc753217.aspx
Set Aging and Scavenging Properties for the DNS Server
The DNS Server service supports aging and scavenging features. These features are
provided as a mechanism for performing cleanup and removal of stale resource records,
which can accumulate in zone data over time. You can use this procedure to set the default
aging and scavenging properties for the zones on a server.
To set aging and scavenging properties for the DNS server using the Windows interface
1. Open DNS Manager.
2. In the console tree, right-click the applicable DNS server, and then click Set
Aging/Scavenging for all zones.
3. Select the Scavenge stale resource records check box.
4. Modify other aging and scavenging properties as needed.