UGC NET Questions (Paper – 1)

Statements A, B and C correctly describe star, bus and ring topologies, whereas D gives an incorrect property of mesh topology. Mesh networks are characterised by multiple possible paths between nodes, which supports redundancy and fault tolerance. Saying that there is only one path contradicts the very idea of a mesh. Therefore, the combination containing A, B and C but not D is the only fully correct option.

Option A:
Option A is correct because it brings together the accurate descriptions of three fundamental topologies without including the misleading statement about mesh networks. It shows that star uses a central device, bus uses a shared backbone and ring uses a closed loop. By omitting D, it avoids confusion about the nature of mesh connectivity.

Option B:
Option B is incomplete because it includes only A and B and leaves out C. While star and bus are important, ring topology is also a standard design and must be acknowledged to answer the question fully. Excluding C means not all correct statements are chosen.

Option C:
Option C is incomplete because it groups B and C but omits A. Star topology is widely deployed in modern LANs, so leaving it out fails to recognise one of the most common practical configurations.

Option D:
Option D is incorrect because it accepts all four statements, thereby treating D as correct. Since mesh topology typically offers multiple routes between nodes, D is false, and its inclusion invalidates this combination.

Statements A, B and C correctly define star, bus and ring topologies as described in networking theory. They specify how nodes connect to hubs, backbones and loops. Statement D is false because some topologies, especially star, can have single points of failure at central devices. Therefore the correct combination is A, B and C only.

Option A:
Option A is incorrect because it lists only A and B as correct and leaves out C. While A and B are true, C is also correct in describing a ring structure. Excluding C produces an incomplete summary of topologies.

Option B:
Option B is incorrect because it suggests A, C and D are correct, thereby accepting D. Statement D contradicts the idea of a central hub or shared cable that can cause widespread disruption if it fails.

Option C:
Option C is incorrect because it groups B and C only and omits A. Since star topology is one of the most common designs, an explanation that leaves it out is inadequate.

Option D:
Option D is correct because it brings together A, B and C as true and excludes D, which overlooks the possibility of single points of failure. This matches standard discussions of network design.

Star topology links each node directly to a central connecting device, so all communication passes through that central point. This layout simplifies fault isolation because a problem in one cable usually affects only one node. It is widely used in modern local area networks with switches. Hence, the topology described in the stem is star topology.

Option A:
Option A, ring, connects devices in a circular fashion where each node has exactly two neighbours, and data travels around the ring rather than through a central node.

Option B:
Option B, bus, uses a single backbone cable to which all devices are attached, and it does not rely on a central connection point.

Option C:
Option C, mesh, involves nodes being interconnected with many redundant paths, which increases reliability but does not match the centralised structure described.

Option D:
Option D is correct because star topology is defined specifically by all nodes connecting to a central device such as a hub or switch.