its obviously A.
case 1 : keep a counter and when it reaches the position k . print the value of kth element. which takes O(k).
case 2: since its difficult to find kth element from the end.you have to keep a counter that counts total number of elements. than find (n-k+1) position than goto that position. O(n) + O(n-k+1) = O(n).
