Which of the following network attacks is the researcher MOST likely experiencing?

A researcher has been analyzing large data sets for the last ten months. The researcher works with colleagues from other institutions and typically connects via SSH to retrieve additional data.

Historically, this setup has worked without issue, but the researcher recently started getting the following message:

Which of the following network attacks is the researcher MOST likely experiencing?
A . MAC cloning
B . Evil twin
C . Man-in-the-middle
D . ARP poisoning

Answer: C

Explanation:

the message is basically saying the known_hosts that your client uses has a tuple that no longer matches this server, usually because the server is presenting a new key to the client, though it could be the same key on a new ip also .

Which could be the result of a MITM attack. (key changed) https://serverfault.com/questions/193631/ssh-into-a-box-with-a-frequently-changed-ip (ip changed)

https://stackabuse.com/how-to-fix-warning-remote-host-identification-has-changed-on-mac-and-linux/