What is the correct process for the TCP three-way handshake connection establishment and connection termination?

FIN, ACK-FIN, ACK describes the connection termination process, not establishment - a FIN segment signals a desire to close a connection, not open one.

While the establishment sequence shown matches SYN, SYN-ACK, ACK, this choice does not include the correct connection termination sequence required to fully answer the question.

ACK, ACK-SYN, SYN is the reverse of the correct establishment sequence and does not correspond to any valid TCP handshake phase.

TCP connection establishment begins with the client sending a SYN segment to synchronize sequence numbers, the server replies with SYN-ACK to acknowledge and synchronize its own sequence, and the client finalizes with an ACK. Connection termination is a separate process using FIN and ACK segments. Answer D correctly pairs the establishment sequence with the proper termination sequence, distinguishing it from the incomplete or incorrectly ordered alternatives.