Final answer:
The Thunderbolt port supports high definition video transmission using the DisplayPort protocol, combining high-speed data transfer and video signals in a single cable.
Step-by-step explanation:
The port that allows for the transmission of high definition video using the DisplayPort protocol is Thunderbolt. The Thunderbolt technology combines PCI Express (PCIe) and DisplayPort (DP) into one serial signal alongside a DC connection for electric power, all in the same cable. While DVI, VGA, and RCA may support video transmission, they do not use the DisplayPort protocol. Thunderbolt ports are often seen on modern computers and enable very high data transfer rates, in addition to carrying high definition video signals.