Quiz: Tree Diameter

The diameter of a tree is the longest path between any $2$ nodes. In a DFS-based solution, you track the $2$ deepest subtrees at each node. Why do you need the $2$ deepest and not just the deepest?

1. A.The second deepest subtree is needed for space complexity reasons
2. B.You need $2$ subtrees to handle the case where the tree is unbalanced
3. C.The deepest subtree alone gives the tree height, not the diameter
4. D.The longest path through a node goes down into $2$ different children, so you combine both depths