The correct answer is C. Cat 6.

An RJ45 connector is a standard type of physical connector for network cables. RJ45 connectors are used almost exclusively with Ethernet cables and networking1. Ethernet cables are twisted pair cables that carry data signals between devices on a network, such as computers, routers, switches, and servers2.

There are different categories of Ethernet cables, such as Cat 5, Cat 5e, Cat 6, and Cat 7, that have different specifications and performance levels. Cat 6 is one of the most common types of Ethernet cables, which supports data transfer speeds up to 10 Gbps and bandwidth up to 250 MHz3. Cat 6 cables have four pairs of copper wires, each with a plastic insulation and a foil or braided shield. The wires are twisted together to reduce crosstalk and interference4.

To terminate a Cat 6 cable, an administrator needs to use an RJ45 connector that matches the wiring scheme of the cable. There are two common wiring schemes for Ethernet cables: T568A and T568B. The administrator needs to strip the cable jacket, untwist the wires, arrange them in the correct order according to the chosen scheme, trim the excess wire, and insert them into the RJ45 connector. Then, the administrator needs to use a crimping tool to secure the wires and the connector4.

Optical cables are not terminated with RJ45 connectors, but with different types of connectors that can transmit light signals, such as SC, ST, LC, or MTRJ connectors. Optical cables are used for fiber-optic networks that can carry data over long distances at high speeds.

Serial cables are not terminated with RJ45 connectors, but with different types of connectors that can transmit serial data signals, such as DB9, DB25, or DE9 connectors. Serial cables are used for connecting devices that use serial communication protocols, such as modems, printers, scanners, or keyboards.

USB cables are not terminated with RJ45 connectors, but with different types of connectors that can transmit universal serial bus data signals, such as USB-A, USB-B, USB-C, or Micro-USB connectors. USB cables are used for connecting devices that use USB communication protocols, such as flash drives, cameras, mice, or chargers.