Your network contains an Active Directory domain named contoso.com. The domain contains a
domain controller named DC1 that runs Windows Server 2012 R2. DC1 has the DHCP Server server
role installed.
DHCP is configured as shown in the exhibit. (Click the Exhibit button.)

You discover that client computers cannot obtain IPv4 addresses from DC1.

You need to ensure that the client computers can obtain IPv4 addresses from DC1.
What should you do?

A.
Activate the scope.

B.
Authorize DC1.

C.
Disable the Allow filters.

D.
Disable the Deny filters.

Explanation:
You have enabled the Allow list but haven’t entered any MAC addresses, thus everyone is denied.
Either Disable the Allow filters or start adding MAC addresses to the Allow filter.
Note: MAC address based filtering allows specific control over which clients have access to DHCP
addresses. You can create a list of computers that are allowed to obtain DHCP addresses from the
server by adding the client MAC address to the list of allowed client computers. By enabling the
allow list, you automatically deny access to the DHCP server addresses to any client computer not on
the list.

DHCP: If the allow list is enabled, MAC address filtering should be populated
https://technet.microsoft.com/en-us/library/ee956897(v=ws.10)