Which of the following options is not true about the binary search tree (BST)?

Correct option is E

A Binary Search Tree (BST) follows three key properties:
1. The left child must have a value smaller than the root node. ✅ (Correct statement)
2. The right child must have a value greater than the root node. ✅ (Correct statement)
3. Both left and right subtrees must also be BSTs (recursive property). ✅ (Correct statement)
Since all statements (a), (b) and (c) are true, there is no incorrect statement in the given options. Thus, option (e) is correct (none of the above are false).
Important Key Points:
1. BST Definition & Structure:
· The left subtree contains only values less than the node.
· The right subtree contains only values greater than the node.
· Both left and right subtrees must also be BSTs.
Example of a BST:
20
/ \
10 30
/ \ \
5 15 40
Knowledge Booster:
· BST operations (search, insert, delete) have O(log N) time complexity in a balanced BST.
· Self-balancing BSTs (AVL Tree, Red-Black Tree) ensure efficient performance by maintaining height balance.
· BSTs are widely used in searching algorithms, range queries and databases (e.g., B-Trees in indexing).