HOTSPOT
You have a domain controller that hosts an Active Directory-integrated zone. On the domain
controller, you run the following cmdlet:
PS C:\> Get-DnsServerScavenging
NoRefreshlnterval:2.00:00:00
Refreshlnterval:3.00:00:00
Scavenginglnterval:4.00:00:00
ScavengingState:True
LastScavengeTime:1/30/2014 9:10:36 AM
Use the drop-down menus to select the answer choice that completes each statement.
Answer: 
Explanation:
Correct:
Refresh and No-Refresh intervals
The next safety valves are the Refresh and No-refresh intervals. Both of these must elapse before a record can be deleted.
The No-refresh interval is a period of time during which a resource record cannot be refreshed. Recall from earlier that a refresh is a dynamic update where we are not changing the host/IP of a resource record, just touching the timestamp. If a client changes the IP of a host record this is considered an “update” and is exempt from the No-refresh interval. The purpose of a No-refresh interval is simply to reduce replication traffic. A change to a record means a change that must be replicated.
After the (Record Timestamp) + (No-refresh interval) elapses we enter the Refresh interval. The refresh interval is the time when refreshes to the timestamp are allowed. This is the time when good things must happen. The client is allowed to come in and update it’s timestamp. This timestamp will be replicated around and the No-refresh interval begins again. If for some reason the client fails to update it’s record during the refresh interval it becomes eligible to be scavenged. Will it disappear immediately? Probably not but it is certainly possible
Source: http://blogs.technet.com/b/networking/archive/2008/03/19/don-t-be-afraid-of-dns-scavenging-just-be-patient.aspx
The No-Refresh interval is the amount of time after the timestamp where the DNS server will not accept a “refresh” from the client.