A binary tree is constructed of nodes that are instances of the following class:

Consider the following method:

You consult three supposedly tech$-$savvy consultants, and you get the following

three opinions about what the method does when passed a reference to the root

node of a binary tree:

I. It returns the last node visited by an inorder traversal

II$.$ It returns the last node visited by a postorder traversal

III. It returns the last node visited by a level$-$order traversal

Which of these opinions is correct regardless of the contents of the tree?

A$.$ I only

B$.$ II only

C$.$ III only

D$.$ I and III

E$.$ II and III