A Transmission Control Protocol (TCP) connection is established and two devices ensure that they're speaking the same protocol. What has occured? A. Three-way handshake
B. Two-way handshake
C. Handshake
D. Four-way handshake

The correct option is;

A. Three-way handshake

Explanation:

For establishment of connection within Transmission Control Protocol, (T. C. P.), involves a three-way way handshake. Prior to attempting a server connection, the server to which connection is sought passively opens a port by listening at the port. Upon establishment of passive open, active open by the client can then be initiated by the client. A connection establishment requires a three-way handshake as follows;

1. The client sends a SYN to the server

2. The server responds by sending a SYN-ACK

3. The client further responds sending ACK back to the server.

so much for the extra points :