Insertion sorting sort all the elements of the array by traversing to each elements in the given array.
But question is given that first k elemenets and last k elements are not sorted so,
it will quick sort who select last elements as pivot and place pivot elements to its correct position
and at left of pivot and right of pivot, elements r still unsorted ........
time compexity is O(n-1)=O(n)
so answer is option (c)