Answer:
d. Merge sort
Explanation:
Merge sort is example of an efficient sorting alogrithm. The Divide and conquer rule is used in this technique. This method breakdown the list into multiple sublists and each sublist contains a single element. This technique merged in the form of sorted lists. This technique uses external memory of the system while sorting.
Merge sort is used to sort the 10,000 items using only 1,000 slots available in the RAM.
