In the context of this exercise, what does it mean if a graph is connected or disconnected?
A graph is connected if there exists a path from every vertex of the graph to every other vertex. If you start at any vertex, you will be able to get to any other vertex in a connected graph.
A graph is disconnected if there are at least two vertices in the graph, such that they are unreachable to each other.
Any graph can be either connected or disconnected, but cannot be both.