What type of cable is used to connect a computer to a router?

The correct choice is the Ethernet cable, as it is specifically designed for network communication and is the standard type of cable used to connect computers to routers. Ethernet cables facilitate data transfer within local area networks (LANs), allowing computers to communicate with each other and access the internet through a router.

In networking environments, Ethernet cables come in various categories, such as Cat5, Cat5e, Cat6, and Cat6a, which differ in speed and performance capabilities but all serve the primary function of connecting network devices. The physical connectors used with Ethernet cables are RJ45 connectors, making them suitable for plugging into both computers and routers.

Other types of cables listed serve different purposes: coaxial cables are used primarily for cable television and cable internet services; HDMI cables connect devices to displays for high-definition audio and video; and serial cables are used for serial communication between devices, like connecting a computer to peripherals or legacy devices, but not for networking. Therefore, Ethernet cables are the appropriate choice for connecting a computer to a router to ensure efficient data communication and internet connectivity.