What is the primary difference between TCP's three-way handshake and UDP?

• A. TCP establishes a connection with a three-way handshake; UDP does not, offering fire-and-forget transmission.
• B. Both use a three-way handshake; UDP adds encryption.
• C. TCP is slower but not connection-oriented; UDP is connection-oriented.
• D. UDP guarantees delivery; TCP does not.

Answer: (A)

The main idea being tested is that TCP is connection-oriented and uses a handshake to establish a session, while UDP is connectionless and sends data without any prior setup. In TCP, the three-way handshake coordinates the start of a connection, aligning sequence numbers and other state so data can be delivered reliably in order. UDP, by contrast, sends datagrams directly without establishing a connection, which means lower overhead and latency but no guaranteed delivery, order, or reliability. That’s why the statement that TCP’s handshake and UDP’s behavior differ in this fundamental way is the best match. The other descriptions don’t fit: UDP does not perform a three-way handshake, TCP is indeed connection-oriented, and UDP does not guarantee delivery while TCP does.