Binary Tree - Part 4

Consider the following method: * public string makestring (Treenode root) if (root == null) return ""'; return makeString (root.getieft ()) + makestring(root.getRight 0); If root points to the root of the following tree what string will be returned by makest ring (root)? "' (an empty string) "FIRST" "SIFRT" "STIRF