2021-021

In a graph, a "tree edge" is an edge that is present in the tree obtained after performing DFS on the graph. Suppose that $k$ tree edges resulted from a depth-first traversal of an $n$-vertex, undirected graph. The number of the connected components in the graph can be calculated as:

1. $k-1$
2. $k$
3. $n-k$
4. $n-k+1$
5. None of the above

Original idea by: Soroor Salavati