Adding/Removing Arcs
lAdding arcs to a ______ that is not a tree may make it into a tree.
lAdding arcs to a ______ that is not a tree will never make it into a tree.
lRemoving arcs from a ______ that is not a tree may make it into a tree.
lRemoving arcs from a ______ that is not a tree will never it into a tree.