How Well Do You Know Trees and Forests in Graph Theory?

• A directed acyclic graph with an underlying undirected graph that is a tree
• A connected acyclic undirected graph (correct)
• An undirected graph with at most one path between any two vertices
• A disjoint union of trees

• An undirected graph with at most one path between any two vertices
• A directed acyclic graph whose underlying undirected graph is a forest
• A directed acyclic graph whose underlying undirected graph is a tree (correct)
• A disjoint union of rooted trees

• A directed acyclic graph whose underlying undirected graph is a forest
• An undirected graph with at most one path between any two vertices
• A disjoint union of rooted trees (correct)
• A directed acyclic graph whose underlying undirected graph is a tree