Explanation:
C: A primary DNS server has the “master copy” of a zone, and secondary DNS servers keep copies of the zone for redundancy. When changes are made to zone data on the primary DNS server, these changes must be distributed to the secondary DNS servers for the zone. This is done through zone transfers. If you allow zone transfers to any server, all the resource records in the zone are viewable by any host that can contact your DNS server. Thus you will need to secure the zone transfers to stop an attacker from mapping out your addresses and devices on your network.