How does DNS security combat CnC callbacks?

How does DNS security combat CnC callbacks?
A . By filtering DNS requests, it blocks all requested zone transfers.
B . By changing the DNS MX field, CnC systems cannot be reached on the outbound connection.
C . By implementing DNS security measures, CnC callbacks over any ports and protocols are blocked when the DNS queries to any bad or malicious domains are prevented.
D . Using openDNS servers, such as Google openDNS (8.8.8.8), DNS requests are filtered based on the IP reputation tables that are maintained.
E . By configuring clients to use cloud-based DNS services, CnC callbacks are originated only in the cloud.

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Answer: C