17 60 5 20 42 105 3 955 You need to delete the root (55), which key will replace it? a) 17 b) 60 c) 55 d) 42 vii) Suppose we need to sort a list of employee records in ascending order, using the social security number (a 9-digit number) as the key (i.e., sort the records by social security number). If we need to guarantee that the running time will be no worse than nlgn, which sorting methodscould we use? a) mergesort b) quicksort e) insertion sort d) Either mergesort or quicksort e) None of these sorting algorithms guarantee a worst-case performance of nlgrn or better vii) Here is a binary search tree: What is the post-order tree traversal sequence? a) 1,3,6, 4, 7, 8, 10, 14, 13