Welcome to your interview.
The question is on your right: TCP FIN Without ACK Behavior. Take a moment with it first.
Talk your thinking through with me if you like - when you're confident, submit your answer and I'll grade it like a real screen (7/10 or better passes). Discussion and graded submissions share your five interviewer interactions, so spend them well.
Explain what will happen if the server sends the FIN to the client while the client does not send an ACK back.