#### Answer

A spanning tree of a graph is a subgraph which contains all of the original vertices, is connected, and does not contain any circuits.

#### Work Step by Step

A graph has vertices and edges. A subgraph is a graph with vertices and edges which are chosen from the set of vertices and edges in the original graph.
A spanning tree of a graph is a subgraph which contains all of the original vertices, is connected, and does not contain any circuits.