Which network topology contains a backbone which runs the length of the network?

The answer is bus. The network topology which contains a backbone that runs the length of the network is called a bus topology. A bus topology is used for a LAN (Local Area Network) where several different nodes are all connected to an individual cable, often called a "backbone".

It is called a backbone because if something goes wrong with the cable that all of the nodes are plugged into, then the entire network will not work. Even though this is a crucial downfall, bus topologies are one of the easiest to use and require very little maintenance compared to other types of network topologies.