You are given a binary search tree, whose keys are integers between 1 and 15. You need to search for 7 in this tree. While searching for 7, which sequence below cannot be the sequence of keys visited?a. 8, 6,7b. 15, 13, 14, 10,7c. 1, 11,2, 9.3, 8, 4,7d. 3, 13, 2, 12,7