The correct answer is C. Transition Network.
A transition network is a network with named nodes and labeled arcs that can be used to represent certain natural language grammars to facilitate parsing. The nodes in a transition network represent states, and the arcs represent transitions between states. The labels on the arcs represent the actions that are taken when the network is in a particular state and a particular arc is traversed.
Tree networks, star networks, and complete networks are all types of graphs. A graph is a collection of vertices (also called nodes or points) and edges (also called links or lines). The vertices in a tree network are connected to each other in a tree-like structure, with each vertex having at most one parent vertex. The vertices in a star network are connected to each other in a star-like structure, with each vertex having exactly one parent vertex. The vertices in a complete network are connected to each other in a complete graph, with each vertex connected to every other vertex.
None of these types of graphs is a good representation of a natural language grammar. A natural language grammar is a set of rules that define the structure of sentences in a language. A transition network is a good representation of a natural language grammar because it can be used to represent the rules of a grammar in a way that is easy to understand and use.