Question: Find a minimum spanning tree of each of these graphs where the degree of each vertex in the spanning tree does not exceed 2.
Let G = (V , E) be a directed graph and let r be a vertex in G. An arborescence of G rooted at r is a sub graph T = (V , F ) of G such that the underlying undirected graph of T is a spanning tree of the underlying undirected graph of G and for every vertex v ∈ V there is a path from r to v in T (with directions taken into account).