In post-order traversal , we've to
- Traverse the left sub-tree of root
- Traverse the right sub-tree of root
- Visit the root
The nodes are visited in post-order as D E B F G C A
& according to the question D E B F G C A equals to ab - cd * +
∴ D = a , E = b , B = - , F = c , G = d , C = * , A = +
write the things sequentially
A = + , B = - , C = * , D = a , E = b , F = c , G = d
∴ the answer is Option B)