In a graph, what are the two fundamental components?

• A. Vertices and edges
• B. Nodes and labels
• C. Paths and weights
• D. Arrays and lists

Answer: (A)

In a graph, the building blocks are vertices (points) and edges (the connections between those points). A vertex represents an object or entity, like a city or a person, and an edge shows a relationship or link between two vertices, such as a road between cities or a friendship between people. This pair defines what the graph looks like and how it can be traversed or analyzed. Features you might encounter—like paths, which are sequences of edges, or weights on edges that indicate costs or distances—exist on top of these two elements and describe behavior or properties, not the fundamental makeup of the graph. Other things, like labels on nodes or entirely different data structures such as arrays and lists, aren’t what define a graph themselves.