What does the 3-way handshake in TCP establish?

Correct answer: A connection state between a client and server

Option D is correct because the TCP three-way handshake (SYN, SYN-ACK, ACK) establishes a reliable, stateful connection between a client and server by synchronizing sequence numbers and confirming both sides are ready to communicate, but it does not provide authentication or encryption by itself. Option A is incorrect because the three-way handshake establishes a connection, not an authenticated session; authentication requires additional protocols such as TLS or application-layer mechanisms. Option B is incorrect because the three-way handshake creates a TCP connection with no encryption; a secure tunnel requires TLS or IPsec layered on top. Option C is incorrect because the three-way handshake is a connection-establishment mechanism, not a file transfer protocol; file transfer uses protocols such as FTP or SFTP that run over an established TCP connection.