Solution

The correct answer is IEJFCGKLHDBA

Given: 

Preorder - ABCEIFJDGHKL

Inorder - EICFJBGDKHLA

Concept:

Since in preorder traversal root is visited first, then left child, later right child.

Explanation:

Given preorder and Inorder we can construct the complete tree as follows:-

we find the root using preorder and we find left and right child using Inorder

New root = B since preorder contains B next.

Now from this tree we find post order traversal, which is IEJFCGKLHDBA