How does DNS Tunneling exfiltrate data?

How does DNS Tunneling exfiltrate data?

A. An attacker registers a domain that a client connects to based on DNS records and sends malware through that connection. B. An attacker opens a reverse DNS shell to get into the client's system and install malware on it. C. An attacker sends an email to the target with hidden DNS resolvers in it to redirect them to a malicious domain. D. An attacker uses a non-standard DNS port to gain access to the organization's DNS servers in order to poison the resolutions.