How does a merge sort algorithm primarily function?

The merge sort algorithm primarily functions by breaking down an unsorted list into smaller sublists. This divide-and-conquer strategy involves recursively dividing the main list into halves until each sublist consists of a single element. Since a single element is inherently sorted, the algorithm then proceeds to merge these sublists back together in a manner that results in a fully sorted list.

The critical aspect of merge sort is its systematic approach to sorting: first, the unsorted list is divided into smaller, more manageable parts, and then these parts are merged in a sorted order. This is where the efficiency of merge sort shines, particularly with larger datasets, as it consistently operates with a time complexity of O(n log n).

While other options mention aspects of data manipulation or alternative sorting techniques, only the breakdown of the list into smaller components captures the essence of how merge sort operates. Without this division, effective merging would not be possible, which is why this strategy is foundational to the merge sort process.