ANS:D
To locate the number 43, draw BINARY SEARCH TREE of the given option by keeping in mind there MUST NOT ANY VIOLATION OF DEFINITION.
OPTION:
a,b,c: Correct Probe Sequence(because No Violation)
d:In BST, you will get right subtree of node 27 contains 66,18,43 (here node 18 must be to the left of parent node 27)
Reference:https://en.wikipedia.org/wiki/Binary_search_tree