What is the difference between the OSI model's 'Connection-Oriented' service and 'Connectionless' service at the Transport layer, and which Transport layer protocol exemplifies each?

• A.Connection-Oriented uses IPv6; Connectionless uses IPv4
• B.Connection-Oriented service (TCP): a logical connection is established before data transfer (3-way handshake), data is sequenced and guaranteed to be delivered in order and reliably (ACKs, retransmission), and the connection is formally terminated (4-way FIN). Connectionless service (UDP): no connection establishment; each datagram is independent; no delivery guarantee, no ordering, no flow control; lower overhead and latency
• C.Connection-Oriented uses dedicated circuits; Connectionless uses packet switching; the OSI model assigns session establishment to Layer 6, one layer above transport. The TCP/IP model defines seven layers, one more than the OSI reference model. UDP guarantees ordered delivery by numbering datagrams at Layer 2. TCP performs logical addressing at the network layer by stamping an IP address into each segment header across vendors