单选题：Merge Sort Revisit

Recall that in the merge sort, we divide the input list into two groups of equal size, sort them recursively, and merge them into one sorted list. Now consider a variant of the merge sort. In this variant, we divide the input list into $$\sqrt{n}$$ groups of equal size, where $$n$$ is the input size. What is the worst case running time of this variant? (You may use the fact that merging $k$ sorted lists takes $$O(m\log k)$$ where $$m$$ is the total number of elements in these lists.)





A.$$O(n \log n)$$
B.$$O(n \log^2 n)$$
C.$$O(n \log n \log\log n)$$
D.None of the other options is correct



答案：A