Which of the following is equivalent to saying a graph GGG is a forest?
Every subgraph of GGG is bipartite.
The chromatic number χ(G)≤2\chi(G) \leq 2χ(G)≤2 and it contains no cycles.
The number of edges m=n−cm = n - cm=n−c, where ccc is the number of connected components.
All of the above.