What is the traversal strategy used in the binary tree?

Answer: a

Explanation: Depth-First Search (DFS) is considered the correct answer for tree traversal. This is because DFS follows the fundamental definition of traversal in trees by visiting nodes according to the parent–child hierarchical structure, as seen in inorder, preorder, and postorder traversals. These methods are intrinsic to the recursive nature of binary trees and directly align with their mathematical representation.

Moreover, DFS is more space-efficient compared to Breadth-First Search (BFS). DFS requires O(h) space, where h is the height of the tree (O(log n) for balanced trees), whereas BFS requires O(n) space in the worst case due to storing nodes level by level in a queue. Due to this efficiency and its strong conceptual alignment with tree structures, DFS is regarded as the standard traversal method in most academic contexts, while BFS is typically treated separately as level-order traversal. Hence, DFS is chosen as the correct answer.