(a) (3%) Explain why a spanning tree contains exactly n-1 edges. (b) (5%) Show that the worst case time complexity of a quick sort is O(n (c) (3%) Heap sort is not stable. Give an example of an input list in which the order of 2) records with equal keys is not preserved. (d) (3%) In a min-max heap, if the root's key is removed, the node with the smallest key value among residual nodes is either a child or grandchild of the root. Why