Star is the easiest network type to add new node. Every node in a star network has it's own cable which is directly connected to the central network (hub) without disrupting current users of the network.
In Bus network there is only one central cable, when a new mode is added, there is disruption of the network.
To add a node in Ring network the ring would be broken because data travels in one direction. This addition will cause disruption of the current network users.
In mesh, there is interconnection of device and node. Each device is added to another device, it is not easy to add new mode in a mesh network.
Star -each node on a star network uses its own cable, which makes it easy to add users without disrupting current ones. adding a node to a bus network can sometimes involve breaking the segment, which makes it inaccessible to all other nodes on the network. this makes answer a incorrect. answer b is incorrect because a true ring network model would require that the ring be broken to add a new device. answer d is incorrect because a mesh topology requires that every device be connected to every other device on the network. therefore, it is quite difficult to expand a mesh network.