What is an Ethernet cross-over cable?

What is the most distinguishing characteristic of an Ethernet cross-over cable?

A) An Ethernet cross-over cable is designed to directly connect Ethernet adapters without the use of a hub or switch.

B) An Ethernet cross-over cable is required when you connect Ethernet adapters to a hub or switch.

C) Ethernet cross-over cables are used in the network core to connect routers and switches.

D) There are no major differences between an Ethernet cable and an Ethernet cross-over cable.