Question 23

Insert the elements 71, 65, 84, 69, 67, 83 into an initially empty BST:

1. Insert 71: Root node at Level 0.
2. Insert 65: $65 < 71$, placed as the left child of 71 (Level 1).
3. Insert 84: $84 > 71$, placed as the right child of 71 (Level 1).
4. Insert 69: $69 < 71$ (left), $69 > 65$ (right), placed as the right child of 65 (Level 2).
5. Insert 67: $67 < 71$ (left), $67 > 65$ (right), $67 < 69$ (left), placed as the left child of 69 (Level 3).
6. Insert 83: $83 > 71$ (right), $83 < 84$ (left), placed as the left child of 84 (Level 2).

The levels of the nodes are:

• Level 0: 71
• Level 1: 65, 84
• Level 2: 69, 83
• Level 3: 67

The element at the lowest level (greatest depth) is 67 at Level 3 (Option B).